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24-01-2002 16:32:47 194.66.1.102
Title of Presentation:
The evolution of substorm enhanced whistler mode waves and their relation to SCEs seen on the
ground.
Presenting Author:
Gary A. Abel
Other author(s):
G. A. Abel, A. J. Smith, N. P. Meredith, and G. D. Reeves
Institute(s) of each author:
British Antarctic Survey, British Antarctic Survey, Mullard Space Science Laboratory, Los Alamos
National Laboratory
Abstract:
Substorm Chorus Events (SCEs) have proved to be a useful indicator of substorm onset. The
events are regularly seen in the data from the VELOX (VLF/ELF Logger Experiment) instrument at
Halley, Antarctica, which has provided a decade of near continuous observations. With the
completion of the ongoing deployment of VELOXnet (a network of 5 VELOX instruments), the
coverage will be extended to all local times. The frequency dispersed signatures of SCEs can
be qualitatively understood in terms of substorm injected, energy dispersed, electrons,
exciting whistler mode waves, which are then ducted to the ground. In this paper we present
the results of a study into 20 case studies of CRRES observations of substorm enhanced
whistler mode waves close to the geomagnetic equator and between 02:00 and 06:00 MLT. The
resonant frequency of the whistler waves depends on both the energy of the injected electron
population and magnetic field strength. Studying the evolution of the enhanced whistler mode
waves on both inbound and outbound passes of CRRES allows the separation of these two effects.
By relating the evolution of whistler mode waves following substorm onset to the signatures
seen on the ground we hope to better understand the various observational characteristics of
SCEs. From these observational characteristics we hope to gain further information regarding
the timing, location and energy of injected electrons, making the 10-year SCE dataset a
powerful statistical tool for substorm research.
Type:
talk
Any special equipment:
No
email:
gaab@bas.ac.uk
Post held by presenter:
Postdoc
IP address
194.66.1.102
04-02-2002 12:33:24 131.111.17.134
Title of Presentation:
Solar Active Regions
Presenting Author:
Helen Mason
Other author(s):
H.E. Mason and G. Del Zanna
Institute(s) of each author:
DAMTP, Univ of Cambridge
Abstract:
Solar active regions dominate the UV and X-ray emission from the Sun during solar maximum.
Their nature is complex. Their large scale structure is evidently defined by closed magnetic
structures forming hot loops of plasma. However, the role played by small scale activity due
to emerging flux is not well established. We have used space observations (SOHO-CDS, TRACE,
YOHKOH) to investigate the physical properties of active regions, to study their development
and the relationship between small scale activity and the larger scale structures. We are
particularly interested in the de-stabilisation of the magnetic structures which leads to
filament eruptions and flares.
Type:
poster
Any special equipment:
email:
hm11@damtp.cam.ac.uk
Post held by presenter:
Academic Staff
IP address
131.111.17.134
08-02-2002 15:23:33 193.61.213.131
Title of Presentation:
Simultaneous mesosphere-thermosphere-ionosphere observations during geomagnetic storms
Presenting Author:
Nanan Balan
Other author(s):
N. Balan(1), S. Kawamura(2), T. Nakamura(2), M. Yamamoto(2), S. Fukao(2), S. Watanabe(3), K.
Igarashi(4), K. Shiokawa(5), Y. Otsuka(5), T.Ogawa(5)
Institute(s) of each author:
(1) Department of Physics, University of Wales, Aberystwyth, SY23 2AX, UK., (2)RASC, Kyoto
University, Uji, Kyoto 611, Japan., (3)Department of Earth and Planetary Sciences, Hokkaido
University, Sapporo 060 0810, Japan., (4)Communications Research Laboratory, 4-2-1 Nakui,
Koganei-shi, Tokyo 184-8795, Japan. (5)STE Laboratory, Nagoya University, Toyokawa 442-8507,
Japan.
Abstract:
Two geomagnetic storms, a moderate storm with SC at 1746 UT on 27 March 2001 and a major storm
with SC at 0050 UT on 31 March 2001, occurred while the MU radar (in alternate meteor and IS
modes), optical instruments and ionosondes at 35°N, MF radar at 45°N and
the 1000 receiver GPS network all in Japan were in operation in one of the MTEC-E
(Mesosphere-Thermosphere Experiments for Coupling studies at Equinoxes) campaigns. The data
collected during the campaign (23 March - 02 April 2001) are used to study the storm-time
changes in the upper atmosphere and ionosphere at mid latitudes, including tides and waves. A
rare occurrence of low-midlatitude aurora was observed over the MU radar (35°N) on
the first night (31 March - 01 April) of the major storm. The MU radar measured meridional
neutral wind velocity and plasma drift velocity are incorporated into the Sheffield
University plasmasphere ionosphere model (SUPIM) to investigate the effects of plasma and
neutral composition changes on the 630 nm airglow intensity, ionospheric peak electron density
and peak height, and GPS-TEC observed during the intense optical activity over the radar.
Type:
talk
Any special equipment:
email:
nab@aber.ac.uk
Post held by presenter:
Other
IP address
193.61.213.131
13-02-2002 15:49:57 194.80.32.12
Title of Presentation:
Mesospheric ozone destruction during a solar proton event
Presenting Author:
M. J. Kosch
Other author(s):
M. J. Kosch(1), L.-R. Harris(1), A. J. Kavanagh(1), S. R. Marple(1), M. W. J. Scourfield(2),
G. Bodeker(3), M. Gaussa(4) and F. Honary(1)
Institute(s) of each author:
(1) Dept. Communication Systems, Lancaster University, Lancaster LA1 4YR, (2) Dept. Physics,
Natal University, Durban 4041, South Africa, (3) National Institute of Water and Atmospheric
Research, Otago, New Zealand, (4) ALOMAR, Andoya Rocket Range, N-8483 Andenes, Norway
Abstract:
For the first time, mesospheric ozone destruction has been imaged from the ground. The
Slow-scan CCD All-Sky Imager (SCASI), located at Skibotn, Norway (69.36 N, 20.33 E), has been
used to observe mesospheric OH(6,2) emissions at 843 nm, which come from 87 3 km altitude.
Simultaneously, absorption data from the Imaging Riometer for Ionospheric Studies (IRIS) has
been used over a large field of view (67.8-70.2 N, 17.75-23.75 E), which covers 240 x 240 km.
On the nights of 24, 27 and 28 November 2000 significant enhancements in the OH emission
corresponded to spatially similar increases in absorption. GOES and ACE satellite data show
this period to correspond to a solar proton event with proton fluxes up to 3 orders of
magnitude above background. TOMS satellite data confirms that during this period the total
column ozone over northern Scandinavia was reduced by up to 100 Dobson Units. Ozone LIDAR
measurements from ALOMAR (69.28o N, 16.01o E) provide additional observations. OH emissions
are not affected by electron precipitation, which SCASI observations has confirmed through
numerous observations. Since the most common mechanism for OH creation is by proton
destruction of ozone, we conclude that our OH images are a proxy for mesospheric ozone
destruction. In addition, simultaneous observations of absorption and OH emissions can be used
to identify absorption related to proton precipitation.
Type:
talk
Any special equipment:
None
email:
m.kosch@lancaster.ac.uk
Post held by presenter:
Academic Staff
IP address
194.80.32.12
13-02-2002 15:53:34 194.80.32.12
Title of Presentation:
HIGH-LATITUDE ARTIFICIAL AURORA FROM EISCAT: A CHRONOLOGY
Presenting Author:
M. J. Kosch
Other author(s):
M. J. Kosch(1), A. J. Kavanagh(1), A. Senior(1), F. Honary(1), S.R. Marple(1), M. T.
Rietveld(2) and T. Hagfors(2)
Institute(s) of each author:
(1)University of Lancaster, Lancaster LA1 4YR, UK.,(2)Max-Planck-Institut fuer Aeronomie,
37191 Katlenburg-Lindau, Germany.
Abstract:
The EISCAT HF-facility is capable of transmitting over 200 MW into the ionosphere below 5.432
MHz using the low gain antenna array. Over 1000 MW above 5.432 MHz is available using the high
gain antenna array. During O-mode pumping soon after sunset, F-region electrons can be
accelerated sufficiently to excite the oxygen atoms and nitrogen molecules, resulting in
observable optical emissions at 630 (O1D), 557.7 (O1S) and 427.8 (N2) nm above EISCAT. Initial
success came on 16 February 1999 with optical recordings by ALIS (Auroral Large Imaging
System) from Sweden. Thereafter, most of the optical data was recorded by DASI (Digital
All-Sky Imager), located in Skibotn, Norway (69.35 N, 20.36 E), which is about 50 km away from
the EISCAT transmitter site. This paper is a chronology of recent successes in producing
artificial aurora, which have features unique to high latitudes. Novel discoveries include:
(1) The O1D emission at 630 nm usually appears near the magnetic field aligned direction
regardless of the HF transmitter beam pointing direction, (2) The optical emission appears
well below the HF reflection altitude as well as the upper-hybrid height, (3) The optical
emission disappears when pumping on a gyro-harmonic frequency, and (4) Annular structures are
produced, which subsequently collapse into blobs, when pumping between the magnetic field dip
and Spitze angles.
Type:
poster
Any special equipment:
None
email:
m.kosch@lancaster.ac.uk
Post held by presenter:
Academic Staff
IP address
194.80.32.12
14-02-2002 09:00:08 130.88.96.65
Title of Presentation:
Coronal heating by relaxation events
Presenting Author:
P K Browning
Other author(s):
P K Browning and R Van der Linden
Institute(s) of each author:
Dept of Physics, UMIST,Royal Observatory of Brussels
Abstract:
Observations suggest that solar coronal heating may be the result of a superposition of
transient heating events over a range of energies with "nanoflares" perhaps at the lower
end. We present a model which predicts energy dissipation by a series of events of varying
size. It is supposed that an energy releasing event is triggered by an ideal MHD instability
such as a kink, with the energy dissipation occurring due to reconnection in the
nonlinear phase. This dissipation can be calculated by assuming that the field relaxes to the
appropriate minimum energy state during this phase, where it is required that magnetic
helicity be conserved., A single looplike structure is considered whose magnetic field is
stressed by slow twiting footpoint motions. The equilibrium is parametrised by a piecewise
constant profile of alpha (the ratio of current density to field). We calculate the marginal
stability booundary for ideal kink modes,taking account of line tying, and then determine the
energy release,due to a relaxation to a minimum energy state at this boundary.
Type:
talk
Any special equipment:
email:
p.browning@umist.ac.uk
Post held by presenter:
Academic Staff
IP address
130.88.96.65
14-02-2002 11:43:12 194.80.32.12
Title of Presentation:
Dynamics of auroral forms and absorption patches during substorm activity
Presenting Author:
Mike Kosch
Other author(s):
C.F. del Pozo, F. Honary, and M.J. Kosch
Institute(s) of each author:
Dept. Communication Systems,Lancaster University,Lancaster, LA1 4YR
Abstract:
Simultaneous observations with the IRIS, DASI and EISCAT systems are employed in the study of
the spatial distribution and temporal evolution of auroral forms and precipitation regions
during substorm activity. The systematic analysis of 2D structures corresponding with well
defined optical and absorption features is presented. The orientation, characteristic lengths
(elongation and width) and the gravity centre of these spatial features are determined and
compared. When substorm onset falls within the common field of view there is a close
correspondence between the optical and the absorption signatures of the auroral forms, as well
as in their overall north-south motion characteristic of the various phases of the substorm.
The motion of arc-like features from DASI is compared with the motion of the estimated
elongation axis of the corresponding absorption region from IRIS. Optical signatures of arcs
are more evenly distributed in space, being narrower and elongated along the L-shells, while
the absorption regions are more structured and patchy, although generally following the arcs
shape and alignment. Moreover, cross-correlation of the time-series of maximum absorption and
maximum green-line emission shows a systematic delay of absorption relative to optical
emission. Time delays are larger for disturbed conditions (40 to 60 s) than for moderately
active conditions (10 to 20 s).
Type:
poster
Any special equipment:
email:
m.kosch@lancaster.ac.uk
Post held by presenter:
Academic Staff
IP address
194.80.32.12
15-02-2002 10:02:58 194.66.147.4
Title of Presentation:
First results from HESSI
Presenting Author:
Andrew Conway
Other author(s):
Andrew Conway,John Brown
Institute(s) of each author:
The Open University,Glasgow University
Abstract:
HESSI - the High Energy Solar Spectroscopic Imager - was launched in Feb 2002 to observe high
energy emission from solar flares (photon energies ~3 keV to 20 MeV). The images and spectra
obtained can tell us about the energetic particles which, arguably, are the first to carry the
enormous energy released from the magnetic field in the early impulsive stages of a flare. I
will review HESSI's first results in the context of the planned campaign of optical, radio and
magnetogram observations.
Type:
talk
Any special equipment:
email:
a.j.conway@open.ac.uk
Post held by presenter:
Academic Staff
IP address
194.66.147.4
15-02-2002 10:16:35 130.246.135.176
Title of Presentation:
Investigating the effect of ion velocity variability on electric field models using EISCAT
data.
Presenting Author:
C. J .Davis
Other author(s):
C. J .Davis and A. D. Aylward.
Institute(s) of each author:
Rutherford Appleton Laboratory,University College, London
Abstract:
Recent work by Codrescu et al has focussed on the role of ion velocity variations in the Joule
heating estimated in coupled models. This work was limited by the monostatic nature of the
Millstone HIll radar and so we have carried out a similar study using tristatic velocity
measurements from the EISCAT UHF radars.
Type:
talk
Any special equipment:
email:
c.j.davis@rl.ac.uk
Post held by presenter:
Other
IP address
130.246.135.176
15-02-2002 13:57:49 155.198.17.120
Title of Presentation:
Magnetic field intensitiy and solar wind speed correlation of events observed by ACE.
Presenting Author:
Mathew J. Owens
Other author(s):
Mathew J. Owens and Peter J. Cargill
Institute(s) of each author:
Space and Atmospheric Physics,Imperial College,Blackett Laboratory,London
Abstract:
The relationship between the magnetic field intensity and speed of solar wind events is
examined using approximately three years of data from the ACE spacecraft. No pre-selection of
CMEs or magnetic clouds is carried out. The correlation between the field intensity and
maximum speed is shown to increase significantly when |B| > 18nT for 3 hours or more. Of the
24 events satisfying this criterion, 50% are magnetic clouds, the remaining half having no
ordered field structure. A weaker correlation also exists between southward magnetic field and
speed. Sixteen of the events are associated with halo CMEs leaving the Sun 2 to 4 days prior
to the leading edge of the events arriving at ACE. Events selected by speed thresholds show no
significant correlation, suggesting different relations between field intensity and speed for
fast solar wind streams and ICMEs.
Type:
talk
Any special equipment:
email:
mathew.owens@ic.ac.uk
Post held by presenter:
Postgrad
IP address
155.198.17.120
15-02-2002 14:02:22 193.61.213.131
Title of Presentation:
Solar EUV flux and the dayside high latitude trough: modelling results and experimental
validation
Presenting Author:
M. H. Denton
Other author(s):
M. H. Denton1, S. E. Pryse1, R. L. Balthazor2, R. W. Sims1,R. J. Moffett2, G. J. Bailey2
Institute(s) of each author:
1. Radio and Space Physics Group, University of Wales, Aberystwyth, UK,2. Space and
Atmosphere Research Group, University of Sheffield, UK
Abstract:
The effects of changing solar EUV flux upon the location and structure of the dayside
high-latitude trough are investigated, using a combination of modelling studies and
experimental ionospheric tomography. An increase in the EUV radiation incident upon the
atmosphere causes thermal expansion and an increase in ionisation. This drives ionospheric
features such as troughs to a greater altitude. However, such behaviour may be further
complicated by consequent changes to the chemical composition of the atmosphere, and the fact
that many of the chemical reactions of importance to the ionosphere are temperature dependent.
Since a complete understanding of the response of ionospheric temperature to changing solar
activity remains elusive, the effects of the above processes upon the dayside high-latitude
trough cannot be predicted. In the present paper results from theoretical modelling using the
Coupled Thermosphere-Ionosphere-Plasmasphere model are compared with experimental tomographic
observations of the ionosphere. Calculations have been performed for low, medium and high
solar activity and compared with tomographic reconstructions of ionospheric electron density,
taken under broadly similar conditions, when geomagnetic activity was low. The results show
that the dayside high-latitude trough is driven polewards, and that the density gradient
equatorwards of the trough increases significantly as solar activity increases. However, the
basic form and structure of the trough are little changed. There is broad agreement between
the CTIP modelling calculations and the experimental tomography observations. Future work
includes an investigation of the tongue of ionisation (TOI) and storm enhanced density (SED)
features.
Type:
talk
Any special equipment:
email:
Post held by presenter:
Postdoc
IP address
193.61.213.131
16-02-2002 04:47:17 161.142.100.81
Title of Presentation:
Recent results on fine scale structures in the high latitude summer mesopauseE V
Presenting Author:
E V Thrane
Other author(s):
E V Thrane, T A Blix, U-P Hoppe, O Lie-Svendsen, B Smiley
Institute(s) of each author:
Andoya Rocket Range,Norwegian Defence Research Establishment,Norwegian Defence Research
Establishment,Norwegian Defence Research Establishment,University of Colorado at Boulder
Abstract:
In recent years a number of campaigns combining sounding rocket and ground-based observations
have been conducted from Andoya Rocket Range (69 N, 11 E) in order to study the fine scale
structures in the mesopause region associated with the presence of Noctilucent Clouds (NLC)
and Polar Mesospheric Summer Echoes (PMSE). The instruments in the sounding rockets provide
measurements of structures in the plasma, the neutral gas and the charged aerosols down to a
fraction of a metre, whereas, sophisticated lidar and radar techniques monitor the same volume
of space from the ground. The paper presents examples of recent observations. The PMSEs must
be caused by small scale fluctuations and/or gradients in the D-region electron density, but
the physical mechanisms responsible for such gradients are not fully understood. Turbulent and
molecular diffusion will act to destroy sharp gradients, but the presence of heavy, charged
aerosols will significantly slow down the diffusion processes. The paper discusses the
possibility that horizontal advection combined with horizontal gradients in the plasma density
can contribute to the radar echoes. The results show that such mechanisms are likely to be of
significance in the MF and HF bands for normal ambipolar diffusion, and that in the presence
of charged aerosols, sufficiently sharp gradients can be produced to reflect even VHF waves.
Type:
talk
Any special equipment:
email:
eivind@rocketrange.no
Post held by presenter:
Academic Staff
IP address
161.142.100.81
17-02-2002 18:48:22 155.198.17.120
Title of Presentation:
Cluster observations of the dayside magnetopause
Presenting Author:
M. W. DUNLOP
Other author(s):
M. Dunlop, A. Balogh, R. Elphic, J.-M. Bosqued, P. Cargill, B. Lavraud, M. Taylor, A. N.
Fazakerley, I. Dandouras, H. Reme.
Institute(s) of each author:
The Blackett Laboratory, Imperial College, Prince Consort Road, London, SW7 2BW U.K.,
,NIS-1, Space and Atmospheric Sciences, Los Alamos National Laboratory, Los Alamos, NM
87545, USA,Centre d'tude Spatiale des Rayonnements, D partement systme solaire, 9 avenue du
Colonel Roche, 31028 Toulouse, Cedex 4, FRANCE,Mullard Space Science Laboratory, Holmbury St.
Mary, Dorking, Surrey, UK
Abstract:
We investigate a number of magnetopause crossings observed by Cluster, including those
relating to regions adjacent to the cusp, in terms of the structure of the boundary layer and
its dynamic response to external conditions. A number of crossings are presented in which the
nature of the current layer, and signatures of magnetic reconnection in the magnetopause
boundary layer are investigated with the four-spacecraft data. The local direction of the
magnetopause current can be determined, for example, and compared to plasma density and
flows. Good knowledge of boundary orientation and motion can accurately scale the plasma and
field signatures across the boundary layer. Spatial structure in transient reconnection
signatures can also be resolved with the four spacecraft information.
Type:
talk
Any special equipment:
email:
m.dunlop@ic.ac.uk
Post held by presenter:
Postdoc
IP address
155.198.17.120
18-02-2002 11:38:26 128.40.84.24
Title of Presentation:
Does the thermosphere pre-condition the ionosphere
Presenting Author:
Anasuya Aruliah
Other author(s):
A. L. Aruliah, E. M. Griffin, A. D. Aylward, I. C. F. Mueller-Wodarg
Institute(s) of each author:
Atmospheric Physics Laboratory, University College London
Abstract:
The energy from the magnetospheric dynamo is dissipated through the high-latitude
thermosphere via the ionosphere. The geomagnetic history of the thermospehre, i.e. the
level of geomagnetic activity experienced in the previous 6-12 hours, significantly modifies
the response of the upper atmosphere. Joule heating is reduced/increased significantly when
the geomagnetic history is previously active/previously quiet. Conversely the current status
of the thermosphere may possibly be used to predict the likely range of response of the upper
atmosphere to geomagnetic forcing. Data are presented from Fabry-Perot Interferometers
measuring thermospheric winds and temperatures that are co-located with the EISCAT and ESR
radars in northern Scandinavia. These are compared with model simulations using the
Coupled Thermosphere Ionosphere Plasmasphere (CTIP) model.
Type:
talk
Any special equipment:
email:
anasuya@apl.ucl.ac.uk
Post held by presenter:
Academic Staff
IP address
128.40.84.24
18-02-2002 14:48:13 144.32.34.86
Title of Presentation:
Observations of a plamaspheric giant pulsation (Pg) at very low latitudes, around L~3.
Presenting Author:
D.K. Milling
Other author(s):
D.K. Milling, I.R. Mann and L.G. Ozeke
Institute(s) of each author:
University of York
Abstract:
An unusual Pc4 ULF pulsation has been observed with both the SAMNET and IMAGE magnetometer
networks as well as with a Doppler receiver at L=2.95. The wave has all the expected
properties of a giant pulsation (Pg) being characterised by its monochromatic appearance and
long duration (> 3 hours). It also exhibits an increase in wave period across the event, from
125 seconds to 144 seconds, which is a commonly observed feature of Pgs. However, this event
is very unusual in that the resonance occurs at L ~ 3 instead of in the usual auroral zone
location. This is well inside the plasmasphere for the prevailing geomagnetic conditions. We
describe the morphology of the event and ask whether the observed wave periods and
propagation characteristics can be explained by current models of Pg generation. In
particular, we test the hypothesis that this event could be driven by drift-bounce resonance
with energetic ions, despite being observed at very low latitudes around L = 3.
Type:
talk
Any special equipment:
no
email:
dave@samsun.york.ac.uk
Post held by presenter:
Postdoc
IP address
144.32.34.86
19-02-2002 09:46:40 155.198.17.120
Title of Presentation:
Cluster Observations of ULF waves in the Terrestrial Foreshock
Presenting Author:
Jonathan Eastwood
Other author(s):
J. P. Eastwood (1), A. Balogh (1), M. W. Dunlop (1), T. S. Horbury (1), I. Dandouras (2)
Institute(s) of each author:
(1) The Blackett Laboratory, Imperial College, London,(2) CESR, Toulouse, France
Abstract:
We present Cluster multi-spacecraft observations of the terrestrial foreshock, the region of
space upstream of the bow shock where reflected beams of ions and electrons interact with the
inflowing solar wind generating in particular ULF waves. The four separate Cluster magnetic
field time series can be combined to determine the direction of propagation of the observed
waves, the results of which can be compared to traditional single-spacecraft wave analysis
techniques based on minimum variance analysis. Cluster Magnetic Field observations of ULF
waves in the foreshock on the 23 April 2001 are presented and analysed to determine the
direction of propagation, wave speed, frequency and wavelength in both the spacecraft and
plasma frame. Plasma data is also used in combination with magnetic field data to show
directly the fast mode nature of these waves.
Type:
talk
Any special equipment:
No
email:
j.p.eastwood@ic.ac.uk
Post held by presenter:
Postgrad
IP address
155.198.17.120
19-02-2002 10:49:49 128.40.72.254
Title of Presentation:
The origin of solar white-light flares
Presenting Author:
Sarah Matthews
Other author(s):
Sarah Matthews, Lidia van Driel-Gesztelyi, Hugh Hudson, Nariaki Nitta
Institute(s) of each author:
(1)MSSL/UCL,(2)MSSL/UCL, Observatoire de Paris, Center for Plasma Astrophysics, K.U.
Leuven,(3)SPRC,(4)LMSAL
Abstract:
The problem of accounting for the continuum emission that is observed in solar flares is
still one which is largely unresolved. These white-light flares place severe constraints on
the energy requirements and transport mechanisms operating in the flare, raising the question
of whether partial or total in-situ heating is required to account for this deep atmospheric
heating. Since it is widely believed that the energy release in solar flares occurs in the
corona and that energy is then transported to the low chromosphere where the optical emission
is produced,most attempts to explain the origin of white-light flares have centred on
canonical mechanisms. However, it has become clear that the spatial and temporal
correspondence between white-light and HXR is not one-to one. In order to identify the factors
that lead to the production of enhanced white-light emission we compare the characteristics
of all of the white-light flares observed by Yohkoh in the period 1991-1992 - a total of
approximately 30 events - with a group of non-white-light flares from the same period.
Type:
talk
Any special equipment:
email:
sam@mssl.ucl.ac.uk
Post held by presenter:
Academic Staff
IP address
128.40.72.254
19-02-2002 10:51:49 143.210.44.216
Title of Presentation:
Solar Influences on Global Circulation
Presenting Author:
Scott England
Other author(s):
Scott England, Neil Arnold
Institute(s) of each author:
University of Leicester (both)
Abstract:
There is compelling statistical evidence of a correlation between indices of solar variability
and long term climate change. The mechanism by which the variability in the solar terrestrial
environment couples into the global climate system is poorly understood. To identify the
underlying principles involved, a series of models have been developed and the effects ofn
solar variability on global circulation patterns have been diagnosed. This presentation
focuses on the two dimensional, zonally averaged models which were used to represent the
middle and upper atmosphere in its most simplified form, with the key driving processes
described by idealised functions, model results and observational data. Simplified meridional
circulation patterns were obtained from these models. Modulating the effects of solar forcing
produces a direct response in the upper atmosphere. The way in which these changes couple into
the circulation patterns and hence the global climate system was observed.
Type:
talk
Any special equipment:
email:
sle5@ion.le.ac.uk
Post held by presenter:
Postgrad
IP address
143.210.44.216
19-02-2002 12:00:20 128.40.71.138
Title of Presentation:
The Science of Solar B
Presenting Author:
Louise Harra
Other author(s):
Louise Harra & Len Culhane
Institute(s) of each author:
Mullard Space Science Lab
Abstract:
Solar-B is due for launch in 2005 on an ISAS (Institute of Space and Astronautical Science) M
V rocket. It will be placed in a polar sun-synchronous orbit. The instrument payload consists
of the Solar Optical Telescope (SOT), X-ray Telescope (XRT) and the EUV Imaging Spectrometer
(EIS). I will discuss the main science goals of solar B and how they can be addressed.
Type:
talk
Any special equipment:
No special equipment.
email:
Post held by presenter:
Academic Staff
IP address
128.40.71.138
19-02-2002 12:40:54 152.78.128.54
Title of Presentation:
Atomic oxygen zones in the winter thermosphere
Presenting Author:
H. Rishbeth
Other author(s):
H. Rishbeth [1] & R. A. Heelis [2]
Institute(s) of each author:
[1] University of Southampton, U. K.,[2] University of Texas at Dallas, U.S.A.
Abstract:
Current theory of the thermospheric general circulation predicts that zones of enhanced atomic
oxygen concentration exist at high midlatitudes in the winter thermosphere,coinciding with
locations of high F2-layer electron density. This paper reports an investigation of
these zones using data from the AE-C satellite.
Type:
talk
Any special equipment:
NO
email:
hr@phys.soton.ac.uk
Post held by presenter:
Academic Staff
IP address
152.78.128.54
19-02-2002 12:55:23 130.246.132.26
Title of Presentation:
Solar Corona During The 2001 Total Eclipse: Analysis of Data From The SECIS Instrument
Presenting Author:
S. J. Chan
Other author(s):
K. J. H. Phillips, D. R. Williams, R. T. J. McAteer, A. C. Katsiyannis, F. P. Keenan, P.
Rudawy, A. Buczylko, P. T. Gallagher
Institute(s) of each author:
CLRC Rutherford Appleton Laboratory, UK,The Queen’s University Belfast, UK,Institute
of Astronomy, University of Wroclaw, Poland,Emergent Technology Services, Inc., Maryland,
USA
Abstract:
The Solar Eclipse Coronal Imaging System (SECIS) consists of a pair of fast-frame CCD cameras
and associated optics that is capable of imaging the solar corona during total eclipses at a
rate of up to 70 frames a second with output digitised to 12 bits. The aim of the instrument
is to look for oscillations or travelling wave motions in the corona that could indicate the
presence of MHD waves possibly important in the coronal heating process. For the 2001 eclipse,
the cameras were set to a frame rate of 39 frames/second, with the cameras viewing the east
limb of the sun. The 2001 eclipse results are being analyzed at Rutherford Appleton
Laboratory, Queen’s University Belfast and the Institute of Astronomy, University of
Wroclaw. This poster paper is a progress report, describing the main procedures involved in
the analysis to get scientifically meaningful results. These are: dark-current subtraction,
flat-fielding of the images, and compensation for slight amounts of image motion. A procedure
in IDL is being written which will accomplish the necessary corrections and will enable a user
to inspect and do detailed analysis of sections of the data. Illustrations are given of the
problems involved and the means used to solve them. SECIS is a collaboration of CCLRC
Rutherford Appleton Laboratory, The Queen’s University Belfast and the Institute of
Astronomy, University of Wroclaw, Poland. It is funded by PPARC, the Leverhulme Trust and the
Polish science funding agency KBN.
Type:
poster
Any special equipment:
email:
s.j.chan@rl.ac.uk
Post held by presenter:
Other
IP address
130.246.132.26
19-02-2002 16:43:21 137.108.72.50
Title of Presentation:
Modelling Solar Magnetic Energy Release using Cellular Automata.
Presenting Author:
Mr Chris Brockwell
Other author(s):
C.P.Brockwell,Dr A.Conway
Institute(s) of each author:
Both are at :,Department of Physics and Astronomy,The Open University,Walton Hall,Milton
Keynes,MK7 6AA
Abstract:
Flaring events occur in the solar atmosphere which, by size of energy release, range over many
orders of magnitude. While MHD and kinetic treatments are becoming increasingly capable of
modelling the overall structure of the magnetic field in a given flare, there also exists
much work on the size distribution of flares and magnetic structures. It remains an open
question as to how to bridge these two regimes of scale and approach. If we suppose that the
details of the unknown physics (e.g. of flare energy release) can be summarised in a few
statistical parameters (e.g. probability of a flare, distribution power law index etc) then
the cellular automata approach provides a possible way forward. Our cellular automata models
use one-dimensional fluid equations,together with parameterized magnetic reconnection.
Specifying only very general initial conditions, a variety of interesting behaviour subject
to interpretation is produced. Some of this data is presented and interpreted here.
Type:
talk
Any special equipment:
No special equipment please.
email:
c.p.brockwell@open.ac.uk
Post held by presenter:
Postgrad
IP address
137.108.72.50
20-02-2002 10:35:28 194.66.2.65
Title of Presentation:
ASSESSING THE ACCURACY OF OPEN-CLOSED FIELD LINE BOUNDARY DETERMINATIONS IN THE CUSP
IONOSPHERE
Presenting Author:
Gareth Chisham
Other author(s):
G.Chisham, M.P.Freeman, M.Pinnock
Institute(s) of each author:
British Antarctic Survey, Cambridge, UK.
Abstract:
The large combined fields-of-view of the SuperDARN HF radar network allows for large-scale
imaging of the magnetospheric system. The Doppler spectral width characteristics of SuperDARN
backscatter are now regularly used to distinguish between the footprints of open and closed
field lines in the cusp ionosphere. The derived open-closed field line boundary can be
combined with appropriate field line mapping to place spacecraft observations into their
magnetospheric context. Determining the boundary in the SuperDARN spectral width
measurements requires distinguishing the transition between two regimes where the spectral
width values come from different, but overlapping, statistical distributions. It is not
always a trivial task to accurately determine the boundary location. This paper assesses the
accuracy of typical techniques for boundary determination and suggests an optimum technique
for determining the boundary location. This technique may also be more generally applicable
to the determination of boundaries between two regions with different statistical
characteristics.
Type:
talk
Any special equipment:
email:
gchi@bas.ac.uk
Post held by presenter:
Other
IP address
194.66.2.65
20-02-2002 11:53:48 152.78.128.52
Title of Presentation:
Long-term solar irradiance and facular variabilty associated with changes in the coronal
source flux
Presenting Author:
Simon Foster
Other author(s):
S. S. Foster, M. Lockwood.
Institute(s) of each author:
S. S. Foster = University of Southampton.,M. Lockwood = University of Southampton, Rutherford
Appleton Laboratory
Abstract:
Monthly values of the coronal source flux have been created dating back untill 1868 using the
geomagnetic aa index (lockwood et al, 1999). These values have been found to correlate well
with with the composite solar irradiance variation compiled from measurements by Virgo, Acrim
I and II, HF and ERBS instrumentation (Frohlich and Lean, 1998). Using the monthly values of
Fs as a proxy for solar irradiance, we were able to reconstruct solar irradiance back to
1868. We have alsocreated a model of PSI (photometric sunspot index) dating back untill 1874,
using sunspot area as a proxy. Combining both of these models we have been able to reconstruct
the facular brightening (including quite sun) variations since 1874. We also continue our
investigation using annual values of coronal source flux and PSI (from sunspot number) to look
at facular behaviour at all times since the end of the Maunder minimum.
Type:
poster
Any special equipment:
email:
ssf@soton.ac.uk
Post held by presenter:
Postgrad
IP address
152.78.128.52
20-02-2002 12:52:55 138.251.201.53
Title of Presentation:
An overview of geometric and physical parameters of propagating disturbances in coronal loops
Presenting Author:
I. De Moortel
Other author(s):
I. De Moortel (1), J. Ireland (2), R.W. Walsh (3), A.W. Hood (1)
Institute(s) of each author:
(1) School of Mathematics and Statistics, University of St,Andrews, North Haugh, St Andrews,
KY16 9SS, Scotland,(2) Emergent Information Technology, Inc. NASA Goddard Space Flight
Center, Mail Code 682.3, Building 26, Greenbelt, Maryland 20771, USA.,(3) Department of
Physics, Astronomy and Maths, University of,Central Lancashire, Preston, PR1 2HE, England
Abstract:
We give an overview of both geometric and physical parameters of propagating disturbances in
coronal loops, using high cadence TRACE data (JOP 83 & JOP144). The majority of these
,outward propagating oscillations are found in the footpoints of large diffuse coronal loop
structures, close to active regions. The disturbances travel outward with a propagation
speed v=120 ± 40 s-1. The variations in intensity are estimated to be of the order
of 2%-5%, compared to the background brightness and they get weaker as the disturbance
propagates along the structure. Using a wavelet analysis, periods in the 280 ± 95
seconds range are found. It is suggested that these oscillations are slow
magneto-acoustic waves propagating along the loop.
Type:
talk
Any special equipment:
email:
ineke@mcs.st-and.ac.uk
Post held by presenter:
Postdoc
IP address
138.251.201.53
20-02-2002 14:57:17 138.251.201.48
Title of Presentation:
Nature of the Magnetic Carpet
Presenting Author:
Clare Parnell
Other author(s):
Institute(s) of each author:
University of St Andrews
Abstract:
The properties of small-scale magnetic concentrations on the solar surface are investigated.
Understanding the nature of these concentrations is important (i) for providing indications
as to how the magnetic fields are generated in the solar interior and (ii) for probing the
behaviour of the magnetic field and energy release in the solar atmosphere. Concentrations
from two distinct regions of quiet Sun are identified and analysed using automated routines
that track magnetic concentrations as seem in MDI data. The distributions of the flux, area,
peak flux density and lifetimes of the concentrations are determined. By sorting the
concentrations into those that are born through emergence or fragmentation and those that die
by cancellation of merging, we calculate the typical lifetimes of the concentrations and
investigate the behaviour of their fluxes, areas and flux densities during their lives.
Type:
talk
Any special equipment:
email:
clare@mcs.st-and.ac.uk
Post held by presenter:
Postdoc
IP address
138.251.201.48
20-02-2002 15:33:38 138.251.201.50
Title of Presentation:
The Topology of Coronal Magnetic Fields
Presenting Author:
Daniel Brown
Other author(s):
Daniel Brown
Institute(s) of each author:
University of St Andrews
Abstract:
The Suns corona and the phenomena within it are dominated by the magnetic field. The structure
of coronal events is very complicated and in order to comprehend them we turn to magnetic
topology for assistance. The fundementals of magnetic topology theory will be presented and
the notion of topological states and bifurcations will be discussed. Applications to coronal
structures as seen by the TRACE and SOHO instruments will be presented and the underlying
topological theory that cause these events will be discussed.
Type:
nopref
Any special equipment:
email:
daniel@mcs.st-andrews.ac.uk
Post held by presenter:
Postdoc
IP address
138.251.201.50
20-02-2002 16:41:50 130.246.132.27
Title of Presentation:
SpaceGRID: "Grids" and the European Space Agency
Presenting Author:
C.H. Perry
Other author(s):
C.H. Perry, S. Dunkin, M. Grande, C.D. Pike and B. Stewart
Institute(s) of each author:
Rutherford Appleton Laboratory
Abstract:
SpaceGRID is an ESA study aimed at identifying the potential benefits of the use of
“Grids” within ESA. Grid technology is a new computing infrastructure that is
aimed at providing uniform access to a set of distributed networked resources that would
otherwise be incompatible. One of the areas included in the study is Solar System Research,
encompassing activities in Solar, Solar Terrestrial and Planetary research. In this case the
main benefits to the community are expected to come from the provision of uniform mechanisms
for the location, manipulation, access and sharing of online data. This presentation
provides a brief overview of the study and reports on the status of the user consultation
and requirements definition phase.
Type:
talk
Any special equipment:
email:
c.h.perry@rl.ac.uk
Post held by presenter:
Other
IP address
130.246.132.27
20-02-2002 19:08:24 193.61.255.25
Title of Presentation:
The Energetic Particle Events of Solar Cycle 23
Presenting Author:
M.J.Birch
Other author(s):
B.J.I.Bromage,J.K.Hargreaves
Institute(s) of each author:
Centre for Astrophysics,University of Central Lancashire,Preston PR1 2HE
Abstract:
The Energetic Particle Events of Solar Cycle
23,-----------------------------------------------,Energetic solar flares are the source of
the solar energetic particle (SEP) events which result in polar cap absorption (PCA)
conditions in the earth's ionosphere. SEP characteristics (e.g. temporal distribution) for
solar cycles 19, 20, 21 and 22 have been thoroughly researched. This research has indicated
that the occurrence of SEP events is most likely around the time of solar maximum, or shortly
afterwards. As we extend SEP observations during solar cycle 23, those SEP characteristics
which affect the delay between the proton production at the source flare site and the
detection of the PCA are of particular interest (e.g. heliolongitude of source flare, CME
associations). As a result of the 'garden hose effect' of the interplanetary magnetic field,
the delay is highly dependent on the heliolongitude of the source flare, maximum delays being
observed for flares with western heliolongitudes. Further, the shock front resulting from the
passage of a CME can re-energise and accelerate the proton flux released from a previous
source flare. The time delay between the occurrence of the flare at the sun and the PCA at
the earth is therefore dependent on (i) the heliolongitude of the flare, and (ii) whether or
not a flare-associated CME is present. This paper extends SEP event coverage by considering
those events which have occurred during the elapsed period of solar cycle 23 (1996 to date).
In particular, the statistical distribution of flare occurrence, heliolongitude and CME
association are discussed for solar cycle 23. A comparison is also made with cycle 22, which
is 'paired' with cycle 23 in terms of the solar dynamo.
Type:
poster
Any special equipment:
email:
mjbirch@uclan.ac.uk
Post held by presenter:
Academic Staff
IP address
193.61.255.25
21-02-2002 10:46:36 128.40.72.254
Title of Presentation:
LONG-TERM HELICITY EVOLUTION IN ACTIVE REGION 8100
Presenting Author:
L.M.Green
Other author(s):
L. M. Green{1}, M. C. López Fuentes{2}, C. H. Mandrini{2}, P. Démoulin{3}, L. van
Driel-Gesztelyi{1,3,4,5}, J. L. Culhane{1}
Institute(s) of each author:
{1}Mullard Space Science Laboratory, UCL, UK,{2}Instituto de Astronomía y Física del
Espacio, IAFE,1428 Buenos Aires, Argentina,{3}Observatoire de Paris, Meudon,
France,{4}Centre for Plasma Astrophysics, Leuven, Belgium,{5}Konkoly Observatory, Hungary
Abstract:
Recent work in the field of coronal mass ejections (CMEs) has involved studies of the
relationship between these ejecta and magnetic helicity. Magnetic helicity quantifies the
twist and writhe of the field and is a well preserved quantity in the solar corona, even
under non-ideal MHD conditions. The diffusion timescale has been shown to be in the order of
105 years (Berger, 1984), but on the short term helicity may be removed from the corona via
CMEs. This work follows the evolution of NOAA active region 8100 during 5 solar rotations
from November 1997 to February 1998. We compute the coronal helicity in AR 8100 under the
linear force-free assumption and also the helicity expelled by CMEs assuming that each CME
forms a magnetic cloud, fit by a standard flux rope model. These computations are then
compared to the helicity injected into the active region by the action of
differential rotation at the photosphere. Active region 8100 exhibits a rotation of
the photospheric polarities, one around the other, during the period of study. This change in
orientation of the active region results in the helicity injection by differential rotation
changing in magnitude and even sign. In the final three rotations differential rotation
depletes the coronal helicity instead of increasing it. The results show that the main source
of helicity needed to account for the CME activity is not found in differential rotation, but
must come from the inherent twist of the flux tube in the portions below the photosphere.
Type:
nopref
Any special equipment:
email:
lmg@mssl.ucl.ac.uk
Post held by presenter:
Postgrad
IP address
128.40.72.254
21-02-2002 11:03:18 130.246.132.26
Title of Presentation:
Historical Geomagnetic Storms
Presenting Author:
D. M. Willis
Other author(s):
D. M. Willis, G. M. Armstrong, C. E. Ault and F. R. Stephenson
Institute(s) of each author:
D. M. Willis University of Warwick,G. M. Armstrong University of Warwick,C. E. Ault University
of Warwick,F. R. Stephenson University of Durham
Abstract:
Comprehensive catalogues of ancient sunspot and auroral observations from East Asia are used
to identify historical geomagnetic storms in the interval AD 20 - AD 1918. There are 273
entries in the sunspot catalogue and 1156 entries in the auroral catalogue. Databases have
been constucted in which the scientific information in these two catalogues is placed in
specific fields. An historical geomagnetic storm is first defined strictly in terms of an
auroral observation that is associated with a particular sunspot observation, in the sense
that the auroral observation occurred within a few days of the sunspot observation. This
approach results in the identification of some ten to twenty historical geomagnetic storms.
Using modern data on sunspots and geomagnetic storms, it is shown that this small number of
historical geomagnetic storms is consistent with predictions based on the fact that the
ancient oriental astronomers probably saw no more than about 1% of the sunspots large enough
to be seen by the unaided eye (under ideal viewing conditions). However, many of the great
geomagnetic storms occurring in the eighteenth and nineteenth centuries are not identified by
this strict definition of an historical geomagnetic storm. Therefore, the possibility of using
just the ancient auroral observations to identify historical geomagnetic storms is examined
critically. It is concluded that most of the great geomagnetic storms in the interval AD 20 -
AD 1918 can be identified using the ancient oriental auroral observations.
Type:
talk
Any special equipment:
No
email:
d.m.willis@rl.ac.uk
Post held by presenter:
Academic Staff
IP address
130.246.132.26
21-02-2002 11:58:21 143.167.6.185
Title of Presentation:
Analysis of solitary waves in the ionosphere using an inverse scattering transform.
Presenting Author:
Dr Julia M. Rees
Other author(s):
R. Balthazor (1), J. M. Rees (1) and W. B. Zimmerman (2)
Institute(s) of each author:
(1) Space and Atmosphere Research Group Department of Applied Mathematics,University of
Sheffield,(2) Department of Chemical and Process Engineering,University of Sheffield
Abstract:
Acoustic-gravity waves in the thermosphere in the form of Large-Scale Travelling Atmospheric
Disturbances (TADs) approximately satisfy the Korteweg-de Vries (KdV) equation,in respect of
a) linear superposition of components with power spectra that are invariants of the motion of
nonlinear dispersive waves, and b) nonlinear filtering. We use the discrete periodic inverse
scattering transform (DPIST) in place of the conventional Fourier techniques to provide a
nonlinear spectral analysis of the far-field effects of a simulated disturbance in the auroral
region producing a family of waves propagating towards the equator. We find that the longest
wavenumber and dominant TAD mode is a soliton.
Type:
talk
Any special equipment:
email:
j.rees@shef.ac.uk
Post held by presenter:
Academic Staff
IP address
143.167.6.185
21-02-2002 12:49:14 155.198.17.120
Title of Presentation:
Characteristics of weak interplanetary shocks and shock-like events
Presenting Author:
J. M. Gloag
Other author(s):
A. Balogh and J. M. Gloag
Institute(s) of each author:
Space and Atmospheric Physics,Imperial College,Blackett Laboratory,London
Abstract:
The variation of magnetic and plasma parameters across the discontinuity of a collisionless
shock wave are clearly understood and presented in MHD theory. The analysis of 116 shock waves
appearing on the Ulysses shock list in the period mid 1996 to the end of 1999 show that in the
cases of the stronger shock waves, measured by the ratio of downstream to upstream magnetic
field magnitudes, this MHD description is adequate. However in the case of many of the weaker
shocks there are events which are not clearly characterised in MHD terms and in these cases
plasma parameters are particularly difficult to interpret. To explore the issues associated
with these very weak shocks further, a set of shock-like events is considered which have shock
characteristics in the high frequency wave data measured by the plasma wave
investigation(URAP) but are not considered to be clearly shock waves purely considering
magnetic and plasma data. These shock-like events are thought to extend the spectrum of
interplanetary shocks at the very weakest end and possibly beyond what should be considered a
collisionless shock wave.
Type:
talk
Any special equipment:
email:
jonathan.gloag@ic.ac.uk
Post held by presenter:
Postgrad
IP address
155.198.17.120
21-02-2002 12:54:48 155.198.17.120
Title of Presentation:
Magnetic Cloud Properties of Interplanetary Coronal Mass Ejections Observed by the Ulysses
Spacecraft
Presenting Author:
A. Rees
Other author(s):
R.J. Forsyth
Institute(s) of each author:
Imperial College of Science, Technology & Medicine
Abstract:
The unique orbit of Ulysses allows an investigation of magnetic clouds, a magnetic signature
of interplanetary cornonal mass ejections, away from the ecliptic plane. We have performed a
survey of magnetic clouds observed by Ulysses from mid 1990 to late 2001 identifying 62
candidates. During this time period Ulysses has completed nearly 2 complete orbits, the first
orbit occurring close to solar minimum and the second around solar maximum., A constant
alpha force free flux rope model has been fitted to the candidate events in order to determine
the properties of these magnetic clouds. Information about the size, shape, chirality and
orientation of the magnetic clouds can all be determined. We present here the orientations of
the magnetic cloud axes and their chirality and compare to in-ecliptic observations.
Type:
talk
Any special equipment:
email:
adam.rees@ic.ac.uk
Post held by presenter:
Postgrad
IP address
155.198.17.120
21-02-2002 14:06:37 143.210.44.215
Title of Presentation:
Magnetosphere-Ionosphere Coupling Current System in Jupiter's Middle Magnetosphere: Dependence
on Height Integrated Ionospheric Pedersen Conductivity and Iogenic Plasma Mass Outflow.
Presenting Author:
Nichols, J.D.
Other author(s):
Nichols, J.D.; Cowley S.W.H.
Institute(s) of each author:
University of Leicester,University Road,Leicester,LE1 7RH
Abstract:
We consider the effect of the jovian ionospheric Pedersen conductivity and iogenic plasma mass
outflow rate on the main jovian auroral oval parameters that have been determined from
steady-state Hill-Pontius theory. Planetary magnetic field models considered are a simple
dipole field and an empirical current sheet field based on fly-by observations. We show that
in the region of Io the dominating factor is the plasma mass outflow rate while at large
distances the dominating factor is the ionospheric Pedersen conductivity. We then use Voyager
1 magnetic field data to estimate the magnitudes of the plasma mass outflow rate and the
ionospheric Pedersen conductivity.
Type:
talk
Any special equipment:
email:
jdn@ion.le.ac.uk
Post held by presenter:
Postgrad
IP address
143.210.44.215
21-02-2002 14:38:52 194.117.133.84
Title of Presentation:
Global coupled model studies of the Jovian upper atmosphere in response to electron
precipitation and ionospheric convection within the auroral region.
Presenting Author:
George Millward
Other author(s):
G H Millward, S Miller, and A D Aylward
Institute(s) of each author:
Atmospheric Physics Laboratory, department of Physics and Astronomy, University College
London.
Abstract:
The Jovian Ionospheric Model (JIM) is a global three-dimensional model of Jupiter's coupled
ionosphere and thermosphere, developed at University College London. Recently, the model has
been used to investigate the atmospheric response to electron precipitation within the
high-latitude auroral region. A series of simulations have been performed in which the model
atmosphere is subjected to monochromatic precipitating electrons of varying number flux and
initial energy and, in addition, to various degrees of ionospheric convection. The auroral
ionospheric conductivity which results is shown to be strongly non-linear with respect to the
incoming electron energy, with a maximum observed for incident particles of initial energy 60
KeV. Electrons with higher energies penetrate the thermospheric region completely, whilst
electrons of lower energy (say 10 keV) produce ionisation at higher levels in the atmosphere
which are less less condusive to the creation of ionospheric conductivity. Studies of the
thermospheric winds with the auroral region show that zonal winds (around the auroral oval)
can attain values of around 70% of the driving zonal ion velocity. Also the results show that
these large neutral winds are limited in vertical extent to the region of large ionospheric
conductivity, tailing off markedly at altitudes above this. The latest results from this work
will be presented, and the implications for Jovian magnetospheric-ionospheric coupling will be
discussed.
Type:
talk
Any special equipment:
email:
george@apl.ucl.ac.uk
Post held by presenter:
Postdoc
IP address
194.117.133.84
21-02-2002 14:53:17 147.188.36.26
Title of Presentation:
Influence of convective overshoot in the BiSON signal?
Presenting Author:
Bernard McCarty
Other author(s):
Bernard McCarty
Institute(s) of each author:
BiSON/HiROS,The University of Birmingham
Abstract:
The Doppler velocity measurements made by the Birmingham Solar Oscillations Network (BiSON)
contain a component that is hypothesised to be due to convective overshoot into the
photosphere. Different positions on the 770nm solar potassium line profile observed by BiSON
are mapped to different heights in the solar atmosphere. The variation over the year of the
location of the operating points of the BiSON spectrometers on the solar line allows for an
investigation of the height dependence of this ‘contamination’. Red and blue wing
velocity residuals have been generated from both sides of the potassium line profile and
differences in phase between the two time-series have been extracted. An analysis of these
phase differences will be discussed
Type:
poster
Any special equipment:
email:
bernard@bison.ph.bham.ac.uk
Post held by presenter:
Postgrad
IP address
147.188.36.26
21-02-2002 14:54:35 128.40.71.10
Title of Presentation:
Evidence for acceleration of outer zone electrons to relativistic energies by whistler mode
chorus.
Presenting Author:
Nigel P. Meredith
Other author(s):
[1] N. P. Meredith, [2] R. B. Horne,[3] D. Summers,[4] R. M. Thorne,[1] R. H. A. Iles,[5] D.
Heynderickx and[6] R. R. Anderson
Institute(s) of each author:
[1] Mullard Space Science Laboratory, University College London, Holmbury St Mary, Dorking,
Surrey, United Kingdom,[2] British Antarctic Survey, Natural Environment Research Council,
Madingley Road, Cambridge, United Kingdom,[3] Department of Mathematics and Statistics,
Memorial University of Newfoundland, St. John's, Newfoundland, Canada,[4] Department of
Atmospheric Sciences, University of California, Los Angeles, U.S.A.,[5] Belgian Institute for
Space Aeronomy, Ringlaan 3, Brussels, Belgium,[6] Department of Physics and Astronomy, The
University of Iowa, Iowa City, Iowa, U.S.A.
Abstract:
We use plasma wave and electron data from the Combined Release and Radiation Effects Satellite
(CRRES) to investigate the viability of a local stochastic electron acceleration mechanism to
relativistic energies driven by gyroresonant interactions with whistler mode chorus. In
particular, we examine the temporal evolution of the spectral response of the electrons and
the waves during the October 9, 1990 geomagnetic storm. The observed hardening of the electron
energy spectra over about 3 days in the recovery phase is coincident with prolonged substorm
activity as monitored by the AE index and enhanced levels of whistler mode chorus waves. The
observed spectral hardening is observed to take place over a range of energies appropriate to
the resonant energies associated with Doppler-shifted cyclotron resonance, as supported by the
construction of realistic resonance curves and resonant diffusion surfaces. Furthermore, we
show that the observed spectral hardening is not consistent with standard radial diffusion
models. These results provide strong circumstantial evidence for a local stochastic
acceleration mechanism, involving the energisation of a seed population of electrons with
energies of the order of a few hundred keV to relativistic energies, driven by wave-particle
interactions involving whistler mode chorus. The results suggest that this mechanism
contributes to the reformation of the relativistic outer zone population during geomagnetic
storms, andis most effective when the recovery phase is characterised by prolonged
substorm activity.
Type:
talk
Any special equipment:
email:
npm@mssl.ucl.ac.uk
Post held by presenter:
Postdoc
IP address
128.40.71.10
21-02-2002 15:10:41 128.40.72.254
Title of Presentation:
Single Source Hard X-Ray Sources and the 'Standard' Model
Presenting Author:
Mr Chris Goff
Other author(s):
Goff,C,Matthews,S,Harra,L
Institute(s) of each author:
Mullard Space Science Lab. (MSSL)
Abstract:
Over one third of all flares imaged by Yohkoh's Hard X-ray Telescope show a single hard X-ray
source in multiple channels. In terms of the 'standard' thick target model the most commonly
expected structure is the double footpoint scenario, which has also been suggested to be the
most often observed. This work aims to study single source events in detail to try to
determine whether they represent unresolved double footpoint emission asymmetric electron
deposition due to magnetic mirroring or a genuine departure from the 'standard' model. We
present initial results combining the Yohkoh data with data obtained from SOHO and the
Nobeyama Radio Observatory.
Type:
talk
Any special equipment:
Overhead Projector
email:
cpg1@mssl.ucl.ac.uk
Post held by presenter:
Postgrad
IP address
128.40.72.254
21-02-2002 15:35:09 138.251.201.84
Title of Presentation:
Transition Region Phenomena: Blinkers and Explosive Events
Presenting Author:
Danielle Bewsher
Other author(s):
D. Bewsher, C.E. Parnell, D.E. Innes
Institute(s) of each author:
University of St Andrews (DB, CEP),Max-Planck-Institut fuer Aeronomie (DEI)
Abstract:
Blinkers are short lived intensity enhancements that are observed in the EUV transition region
lines. They were discovered and manually discovered by Harrison (1997) using SOHO/CDS data.
More recently, Bewsher, Parnell and Harrison (2002) and Parnell, Bewsher and Harrison (2002)
have observed blinkers in both quiet and active regions using their automated identification
procedure (BLIP). The key characteristics of blinkers will be discussed and a comparison to
explosive events will be made.
Type:
nopref
Any special equipment:
email:
danielle@mcs.st-andrews.ac.uk
Post held by presenter:
Postgrad
IP address
138.251.201.84
21-02-2002 16:10:13 144.32.128.132
Title of Presentation:
A combined magnetometer and STARE radar study of a travelling convection vortex current system
Presenting Author:
P. R. Abernethy
Other author(s):
P.R. Abernethy, I. R. Mann
Institute(s) of each author:
The University of York
Abstract:
Travelling Convection Vortices (TCVs) are localised convection cells that appear in the
pre-noon or post-noon sectors of the high-latitude ionosphere and move away from local noon in
a predominantly anti-sunward direction. The STARE radar, in conjunction with the IMAGE
magnetometer network, has been used to characterise the properties of a TCV current system in
the ionosphere for an event on 14th December, 1999. Early models (e.g. Glassmeier (1992),
Southwood and Kivelson (1990)) regarded TCVs as a disturbance propagating along the
magnetopause in response to a sudden change in the solar winds dynamic pressure. Recent
observations (e.g Yahnin and Moretto (1996)) suggest that the current centres of TCVs
propagate along closed magnetic field lines deep within the magnetosphere and this has been
incorporated into an MHD model by Slinker et al.(1999). The results from the STARE radar and
IMAGE magnetometers for this event will be compared to the predictions of the Slinker model.
Type:
talk
Any special equipment:
email:
pra100@york.ac.uk
Post held by presenter:
Postgrad
IP address
144.32.128.132
21-02-2002 17:55:38 143.210.44.237
Title of Presentation:
HF coherent radar spectral width and its relationship to the flow reversal boundary.
Presenting Author:
Emma Woodfield
Other author(s):
E.E. Woodfield (1), K. Hosokawa (2), S.E. Milan (1), N. Sato (3), and M. Lester (1).
Institute(s) of each author:
(1) University of Leicester, U.K.,(2) Kyoto University, Japan.,(3) National Institute of Polar
Research, Japan.
Abstract:
The Doppler spectral width parameter routinely produced by the Super Dual Auroral Radar
Network (SuperDARN) has been investigated for its potential use as an ionospheric proxy for
the open/closed field line boundary. A statistical comparison of the spectral width with the
flow reversal boundary has been conducted using three years of data. The regions of broadest
spectral width are found both equatorward and poleward of the flow reversal boundary.
Type:
talk
Any special equipment:
email:
eew4@ion.le.ac.uk
Post held by presenter:
Postgrad
IP address
143.210.44.237
21-02-2002 18:03:52 128.40.84.24
Title of Presentation:
Auroral zone and polar cap thermospheric neutral temperatures: models and measurements.
Presenting Author:
Eoghan Griffin
Other author(s):
E. M. Griffin, A. L. Aruliah, A. Aylward, I. C. F. Mueller-Wodarg
Institute(s) of each author:
Atmospheric Physics Laboratory,University College London
Abstract:
Neutral temperature measurements are necessary in order to study the energetics of the high
latitude thermosphere, indicating the presence of significant events such as the joule
heating resulting from ion-neutral coupling. Direct measurements of thermospheric neutral
temperatures by Fabry Perot Interferometers (FPIs) from sites in the auroral zone (Kiruna)
and polar cap (Svalbard) are used to demonstrate the limitations of both models and
alternative temperature derivation techniques at these latitudes. This is important to
establish the most useful source for neutral temperatures when direct FPI measurements are
not available as neither the absolute value or reaction to solar and geomagnetic conditions
is well represented at high latitudes at present in the MSIS model. The co-location of the
FPIs with the EISCAT and ESR radars allows extensive inter-comparison of experimental data
and this is combined with both empirical and theoretical model data.
Type:
talk
Any special equipment:
email:
eoghan@apl.ucl.ac.uk
Post held by presenter:
Postdoc
IP address
128.40.84.24
22-02-2002 07:10:17 216.147.138.58
Title of Presentation:
STUDIES OF STORM DUSK EFFECT AT HIGH AND LOW SOLAR ACTIVITIES
Presenting Author:
Chandu Venugopal
Other author(s):
K Unnikrishnan(1), Chandu Venugopal(2) and N Balan(3)
Institute(s) of each author:
(1)Department of Physics, N S S Hindu College, Changanacherry - 686-102, Kerala,
INDIA.,(2)Department of Physics, University of Asmara, P O Box 1220,Asmara,
ERITREA.,(3)Department of Physics (Radio & Space Physics Group), University of
Wales,Abersytwyth, Ceredigion SY23 3BZ, Wales, UNITED KINGDOM
Abstract:
Earlier studies have shown large increases in ionospheric peak electron density (N_(m)F_(2))
and total electron content (TEC)in the afternoon-evening hours during geomagnetic storms, and
called it the "storm dusk effect". In the present paper we report the latitudinal, seasonal
and solar activity dependence of the storm dusk effect by studying storm-time TEC data from
low (Ramey: geogra.,lat.16.0 deg. N, geomag. lat. 28.7 deg. N, geomag. long.,293deg. E), mid
(Sagamore Hill: 38.0 deg. N, 50.0 deg. N,289 deg. E) and high (Goose Bay: 48.0 deg. N, 58.6
deg. N,298 deg. E) latitude stations. The study shows that in the winter and equinox of solar
maximum, the strength of the storm dusk effect becomes a maximum at mid-latitudes. However, at
solar minimum it becomes a maximum at mid-latitudes in winter and low latitudes at equinox. In
summer, the effect becomes a maximum at low latitudes for all levels of solar activity.
Comparing the dusk effect in winter and summer, the effect at all latitudes is more
predominant in summer than in winter at solar maximum, and an opposite winter/summer
difference occurs at solar minimum. The dusk effect is found to increase with the intensity of
the geomagnetic storms at all latitudes at solar maximum, and that is found to happen only at
low latitudes during solar minimum. A time delay is found for the maximisation of the storm
dusk effect from high to low latitudes at solar maximum, which is absent at solar minimum. It
is also found that the time delay has no direct dependence on strength of the dusk effect or
the intensity of the geomagnetic storm.
Type:
poster
Any special equipment:
email:
cvg@phys.uoa.edu.er
Post held by presenter:
Academic Staff
IP address
216.147.138.58
22-02-2002 10:18:43 138.251.201.58
Title of Presentation:
Evolution of the Sun's Open Magnetic Flux
Presenting Author:
Duncan H Mackay1
Other author(s):
E.R. Priest1,M. Lockwood2
Institute(s) of each author:
1 University of St. Andrews, North Haugh, St. Andrews, Fife, KY16 9SS,2 World data Centre
C-1 for STP, RAL, Chilton, England
Abstract:
The evolution of the Sun's open magnetic flux is considered through magnetic flux transport
simulations. For single magnetic bipoles it is shown how the open magnetic flux can vary
depending on the initial tilt angle of the bipole. For the majority of tilt angles it is
found that,the open flux may increase past it's intial value due to the effect of diferential
rotation. Full solar cycle simulations are carreid out for 8 cycles to determine how the open
flux varies as many bipole interact.
Type:
talk
Any special equipment:
email:
duncan@mcs.st-and.ac.uk
Post held by presenter:
Postdoc
IP address
138.251.201.58
22-02-2002 10:21:37 193.61.213.130
Title of Presentation:
Evolution with
heliocentric distance of turbulent-scale irregularities in the solar wind
Presenting Author:
R.A. Fallows
Other author(s):
R.A. Fallows, P.J.S. Williams and A.R. Breen
Institute(s) of each author:
University of Wales, Aberystwyth
Abstract:
Interplanetary scintillation (IPS) arises from the scattering of radio waves from a distant
compact source by density irregularities in the solar wind and has been used for many years
to observe the solar wind over a wide range of solar distances and latitudes. The power
spectra of such observations have a magnitude and a frequency cut-off which is related to
the modulation of electron concentration and scale size of these density irregularities in
the solar wind. In this paper the variation of the scintillation index, scale size and shape
of these irregularities with distance from the Sun is investigated.
Type:
talk
Any special equipment:
email:
raf@aber.ac.uk
Post held by presenter:
Postdoc
IP address
193.61.213.130
22-02-2002 10:28:55 193.61.213.130
Title of Presentation:
Random transverse velocities in the solar wind derived from interplanetary scintillation
measurements
Presenting Author:
A.R. Breen
Other author(s):
A. Canals, A.R. Breen and L. Ofman
Institute(s) of each author:
University of Wales, Aberystwyth
Abstract:
Interplanetary scintillation measurements can yield estimates of a large number of solar wind
parameters, including bulk flow speed, variation in bulk velocity along the observing path
through the solar wind and random variation in transverse velocity. This last parameter is
of particular interest, as it can indicate the flux of low-frequency Alfvén waves, the
dissipation of which has been proposed as an acceleration mechanism for the fast solar wind.
Analysis of IPS data is, however, a significantly under-determined problem and a variety of
a priori assumptions must be made in interpreting the data. We have used observations of
simple point-like radio sources made with EISCAT between 1994 and 1998 to estimate random
transverse velocities in the fast solar wind. The results suggest random transverse
velocities close to the Sun which are inconsistent with a WKB solar wind.
Type:
poster
Any special equipment:
email:
azb@aber.ac.uk
Post held by presenter:
Academic Staff
IP address
193.61.213.130
22-02-2002 10:39:48 193.61.213.130
Title of Presentation:
Large-scale structure of the solar wind during the Ulysses fast latitude scan - the view from
interplanetary scintillation measurements
Presenting Author:
A.R. Breen
Other author(s):
A. Canals, A.R. Breen, P. Riley and A.J. Lazarus
Institute(s) of each author:
University of Wales, Aberystwyth
Abstract:
The solar maximum solar wind is highly structured in latitude, longitude and in time. Coronal
measurements show a very high degree of variability, with large variations which are less
apparent in in-situ spacecraft measurements. Interplanetary scintillation (IPS) observations
from EISCAT, covering distances from 20 to 80 solar radii (R) can be used to cast light on
the evolution of the solar wind with heliocentric distance. We present results from EISCAT
IPS measurements made over two intervals (May and September- October 2002) during the second
Ulysses fast latitude scan and compare them with velocities measured in-situ by the Wind and
Ulysses spacecraft.
Type:
poster
Any special equipment:
email:
azb@aber.ac.uk
Post held by presenter:
Academic Staff
IP address
193.61.213.130
22-02-2002 10:58:48 143.167.6.18
Title of Presentation:
Compressional waves in magnetosphere
Presenting Author:
I. Ballai
Other author(s):
I. Ballai
Institute(s) of each author:
Space and Atmosphere Research Center,Dept. of Applied Mathematics,Hicks Building, Hounsfield
Road,Sheffield, S3 7RH
Abstract:
Small-amplitude compressional magnetohydrodynamic-type waves are studied in the
magnetosphere, treated as a rarefied plasma with anisotropy in the kinetic pressure
distribution. The parallel and perpendicular pressures are defined by general polytropic
pressure laws. This double-polytropic model can be considered as a natural extension of the
magnetohydrodynamic (MHD) model when the plasma is collisionless. Generalized linear
dispersion relations for surface and body waves are derived and analyzed for an isolated
magnetic slab. The waves are confined to the slab. For specific polytropic indices, the
results obtained in the (i) Chew-Goldberger-Low (CGL) double-adiabatic and (ii)
double-isothermal approximations are recovered.
Type:
talk
Any special equipment:
email:
i.ballai@sheffield.ac.uk
Post held by presenter:
Postdoc
IP address
143.167.6.18
22-02-2002 11:21:24 155.198.17.120
Title of Presentation:
The heliospheric magnetic field from pole to pole at solar maximum
Presenting Author:
R. J. Forsyth
Other author(s):
R. J. Forsyth, A. Balogh, G. H. Jones, E. J. Smith
Institute(s) of each author:
Authors 1-3: Imperial College, London,Author 4: Jet Propulsion Laboratory, Pasadena, USA
Abstract:
The Ulysses spacecraft has recently performed a fast latitude survey of the heliosphere from
the south polar regions in November 2000 to the north polar regions in October 2001. We report
on the structure of the heliospheric magnetic field during this time close to the maximum of
solar activity. When Ulysses traversed the south polar regions both magnetic field polarities
were encountered at the highest latitudes and the structure of the field was complicated by
dynamical interactions of solar wind streams of different origin and speed. However, by the
time the spacecraft reached the northern polar regions a unipolar region of magnetic field had
become established consistent with the reversal of the underlying solar magnetic field having
taken place. The magnetic field structure was much simpler, consistent with being immersed in
a fast solar wind stream coming from a re-established north polar coronal hole, although
transient disturbances due to coronal mass ejections were still encountered at all latitudes.
Type:
talk
Any special equipment:
No.
email:
r.forsyth@ic.ac.uk
Post held by presenter:
Academic Staff
IP address
155.198.17.120
22-02-2002 11:31:12 143.167.6.18
Title of Presentation:
Compressional waves in the magnetosphere
Presenting Author:
I. Ballai
Other author(s):
I. Ballai, R. Erdelyi
Institute(s) of each author:
Space and Atmosphere Research Center,Dept. of Applied Mathematics,Hicks Building, Hounsfield
Road,Sheffield, S3 7RH
Abstract:
Small-amplitude compressional magnetohydrodynamic-type waves are studied in the
magnetosphere, treated as a rarefied plasma with anisotropy in the kinetic pressure
distribution. The parallel and perpendicular pressures are defined by general polytropic
pressure laws. This double-polytropic model can be considered as a natural extension of the
magnetohydrodynamic (MHD) model when the plasma is collisionless. Generalized linear
dispersion relations for surface and body waves are derived and analyzed for an isolated
magnetic slab. The waves are confined to the slab embedded in a magnetic environment. For
specific polytropic indices, the results obtained in the (i) Chew-Goldberger-Low (CGL)
double-adiabatic and (ii) double-isothermal approximations are recovered.
Type:
talk
Any special equipment:
email:
i.ballai@sheffield.ac.uk
Post held by presenter:
Postdoc
IP address
143.167.6.18
22-02-2002 11:49:25 194.66.1.192
Title of Presentation:
A multi-spacecraft study of field line draping at the magnetopause
Presenting Author:
Iain J Coleman
Other author(s):
Iain J Coleman
Institute(s) of each author:
British Antarctic Survey
Abstract:
The orientation of magnetic field lines in the magnetosheath may be crucial in controlling
the rate and location of magnetic reconnection on the dayside magnetopause. The field
direction in the sheath is related to that observed upstream in the solar wind by field line
draping. This paper presents the results of a multi-spacecraft study, in which IMF
orientations in the solar wind are compared with those measured by spacecraft crossing the
magnetopause. Data from over 30 such crossings, covering a broad range of magnetopause
locations including the subsolar region, flanks and high latitude regions, are combined to
give a statistical picture of draping as a function of solar wind conditions and position on
the magnetopause.,
Type:
poster
Any special equipment:
No
email:
ijc@bas.ac.uk
Post held by presenter:
Postdoc
IP address
194.66.1.192
22-02-2002 11:55:59 143.210.44.150
Title of Presentation:
The role of atmospheric gravity waves in amplifying the solar modulation of the winter
stratosphere.
Presenting Author:
N.F. Arnold
Other author(s):
N.F. Arnold, T.R. Robinson and J. Fan
Institute(s) of each author:
Radio and Space Plasma Physics Group,Department of Physics and Astronomy,University of
Leicester
Abstract:
Wave transport plays a crucial role in maintaining the Earth’s climate system. Whilst
planetary scale wave processes dominate in the stratosphere, smaller scale buoyancy, or
gravity, waves are the most important factor in the mesosphere. Recent observational evidence
indicates a systematic reduction in gravity wave fluxes in the upper mesosphere and lower
thermosphere from solar minimum to solar maximum. We use a three-dimensional model of the
middle and upper atmosphere to show that this change may significantly enhance the coupling
that exists between the solar variability and the winter stratosphere due to planetary wave
activity alone.
Type:
talk
Any special equipment:
None
email:
nfa1@ion.le.ac.uk
Post held by presenter:
Academic Staff
IP address
143.210.44.150
22-02-2002 12:06:12 152.78.128.52
Title of Presentation:
Novel studies of magnetopause reconnection using hydrogen emissions in the cusp.
Presenting Author:
K. Throp
Other author(s):
B.S. Lanchester (1), K. Throp (1), M. Lockwood (1,2), H. Frey (3).
Institute(s) of each author:
(1) Department of Physics and Astronomy, Southampton University, Southampton, SO17 1BJ,(2)
Rutherford Appleton Laboratory, Chilton, Didcot, Oxfordshire, UK.,(3) Space Science
Laboratory, University of California, Berkeley, California, USA.,
Abstract:
We present effects on the cusp ionosphere, as monitored by the IMAGE satellite, of
short-lived temporal changes in the IMF. The cusp is defined in the intensity of the
lyman-alpha proton emission. We invesitigate three ways in which reconnection could explain
these observations. These invoke (1) changes in the position of the reconnection site, (2)
changes in the flux of injected magnetosheath protons and (3) changes in the IMF clock angle
and consequent effects on the acceleration of particles as they cross the magnetopause. In
general a combination of these effects may be active. This study emphasizes the need for
coincident ground-based measurements of proton spectral signitures.
Type:
talk
Any special equipment:
email:
kt395@soton.ac.uk
Post held by presenter:
Postgrad
IP address
152.78.128.52
22-02-2002 12:12:54 193.63.77.32
Title of Presentation:
Spatial and temporal electron density variation off-limb
Presenting Author:
IGNACIO UGARTE-URRA
Other author(s):
GERRY DOYLE,MARIA MADJARSKA
Institute(s) of each author:
Armagh Observatory.
Abstract:
Determination of the spatial and temporal electron density variation off-limb using the CDS
(SOHO) coronal intensity line ratio SiX 356.01/ SiX 347.4
Type:
poster
Any special equipment:
email:
iuu@star.arm.ac.uk
Post held by presenter:
Postgrad
IP address
193.63.77.32
22-02-2002 12:14:32 147.188.36.27
Title of Presentation:
Solar cycle variation of the He II ionization signature
Presenting Author:
Graham Verner
Other author(s):
Graham Verner
Institute(s) of each author:
University of Birmingham
Abstract:
The sharp variation in the adiabatic exponent at the second helium ionization zone creates a
characteristic signal in the solar p-mode eigenfrequencies. This signal carries information
regarding the properties of the region and has been used to map changes in the acoustic depth
and width of the zone with solar activity. This has been undertaken using data from both the
BiSON and GONG observational programmes.
Type:
nopref
Any special equipment:
email:
gav@bison.ph.bham.ac.uk
Post held by presenter:
Postgrad
IP address
147.188.36.27
22-02-2002 12:17:57 138.251.201.64
Title of Presentation:
The Structure of the Magnetic Carpet
Presenting Author:
Robert M Close
Other author(s):
R.m.Close, E.R.Priest, C.E.Parnell, D.S.Brown, D.H.Mackay
Institute(s) of each author:
All are at University of St Andrews
Abstract:
An observed MDI magnetogram is used to determine the topology and the spectrum of fieldline
lengths in the quiet Sun. The topology and lengths of fieldlines are calculated by modelling
the magnetogram by a series of sources and calculating the overlying potential field.
Type:
poster
Any special equipment:
email:
Post held by presenter:
Postgrad
IP address
138.251.201.64
22-02-2002 12:19:08 138.251.201.78
Title of Presentation:
Topology of Coronal Magnetic Fields
Presenting Author:
David Pontin
Other author(s):
D. Pontin, E.R. Priest
Institute(s) of each author:
University of St Andrews
Abstract:
There are eight different topologies for coronal magnetic fields that may arise from three
flux sources in the photosphere, and many more (as yet unclassified) due to four sources. We
develop a theory for understanding bifurcations between these topologies and the way in which
null points of various types occur.
Type:
poster
Any special equipment:
email:
davidp@mcs.st-and.ac.uk
Post held by presenter:
Postgrad
IP address
138.251.201.78
22-02-2002 12:19:57 138.251.201.72
Title of Presentation:
Magnetic field model of SXRs sigmoids
Presenting Author:
Laura Carcedo
Other author(s):
L. Carcedo, A.W. Hood and D.S. Brown
Institute(s) of each author:
Institute of Mathematics, University of St. Andrews
Abstract:
Coronal Mass Ejections tend to originate in strong magnetic field regions of the Sun's corona
that are "sigmoidal" in shape. In these regions, the magnetic field stores energy via
helicity, producing S-shaped loops called sigmoids. When critical conditions are reached,
these sigmoids become unstable and erupt, losing some of the complexity (and hence some of
their magnetic energy) or even disappearing completely. Since these sigmoids are related to
the helicity in the magnetic field, it is important to undertake a comparison between the
magnetic field before and after the eruptions. Using SOHO-MDI magnetograms and an
alpha-constant force-free field model, we are modelling the S-shaped structures seen in
Yohkoh-SXT. Information about the topology of the field,the energy and the magnetic helicity
gives us a hint about the relationship between CMEs and sigmoids.
Type:
poster
Any special equipment:
email:
laura@mcs.st-and.ac.uk
Post held by presenter:
Postgrad
IP address
138.251.201.72
22-02-2002 12:37:34 130.246.132.26
Title of Presentation:
Long-term variations in solar magnetic fields and potential effects on terrestrial climate
Presenting Author:
M. Lockwood
Other author(s):
Institute(s) of each author:
Rutherford Appleton Laboratory,and Southampton University
Abstract:
The long-term variation of open solar flux has been estimated using observations of
geomagnetic activity and the constancy of the radial component of the heliospheric field, as
discovered by the Ulysses satellite. The recent second perehelion pass of Ulysses confirms
that this result holds at solar maximum as well as at solar minimum and allows the
uncertainties introduced by its use to be evaluated. The open solar flux derived is highly
anticorrelated with the flux of cosmic rays reaching Earth. Recent paleoclimate studies have
shown that cosmogenic isotopes, produced in the atmosphere by cosmic ray bombardment, show a
strong correlation with climate indicators throughout the holecene. These results imply that
either cosmic rays can directly influence climate (presumably via the proposed modulation of
low-altitude cloud cover) or that the total solar irradiance is highly correlated with the
open solar flux. Studies over the last 3 solar cycles reveal that the latter may indeed be the
case,and a model developed to explain the open flux variation offers a potential explanation.
Type:
talk
Any special equipment:
PC projector
email:
m.lockwood@rl.ac.uk
Post held by presenter:
Academic Staff
IP address
130.246.132.26
22-02-2002 13:35:34 143.210.44.198
Title of Presentation:
Using power law electron energy distributions to understand FAST satellite flux signals during
an EISCAT heating experiment
Presenting Author:
Miss S.R. Cash
Other author(s):
S.R. Cash1; J.A. Davies1; E. Kolesnikova1; T.R. Robinson1;,D.M. Wright1; T.K. Yeoman1; R.J.
Strangeway2.
Institute(s) of each author:
1=University of Leicester,2=University of California
Abstract:
During a heating experiment carried out on 8 October, 1998, the first detection of
artificially excited ULF waves by satellite (FAST) was achieved. The ULF wave was created by
modulated heating of the auroral electrojet. A number of features of the physical processes
involved, such as the generation process and the Alfvenic wave propagation out of the
ionosphere have been satisfactorily understood, and have been previously reported. However,
there remain a number of puzzling features, epecially those associated with the energy
dispersed downward electron fluxes which are accelerated by parallel electric fields
associated with the wave. However, the results of a new analysis, presented here, have
established that the observations are consistent with a power law electron energy
distribution.
Type:
talk
Any special equipment:
email:
srcash@ion.le.ac.uk
Post held by presenter:
Postgrad
IP address
143.210.44.198
22-02-2002 13:54:59 137.205.8.2
Title of Presentation:
Heating of Coronal Loops by Wide Spectrum Slow Waves
Presenting Author:
V.M. Nakariakov
Other author(s):
V.M. Nakariakov, D. Tsiklauri
Institute(s) of each author:
University of Warwick
Abstract:
A model interpreting upward propagating variations of EUV brightness in solar coronal loops as
slow magnetoacoustic waves is developed. It is shown that wide spectrum slow magnetoacoustic
waves, consistent with currently available observations of the low frequency part of the
spectrum, can provide the rate of heat deposition sufficient to heat the loop. In this
scenario, the heat would be deposited near the loop footpoints,which agrees with the
observationally determined heating function for EUV coronal loops.
Type:
talk
Any special equipment:
email:
valery@astro.warwick.ac.uk
Post held by presenter:
Academic Staff
IP address
137.205.8.2
22-02-2002 14:39:29 137.205.8.2
Title of Presentation:
A Three Dimensional Alfvenic Pulse in a Transversely Inhomogeneous Medium
Presenting Author:
David Tsiklauri
Other author(s):
D. Tsiklauri and V.M. Nakariakov
Institute(s) of each author:
University of Warwick, England
Abstract:
Interaction of incompressible and compressible MHD fluctuations on a one-dimensional plasma
inhomogeneity, transverse to the magnetic field, is considered in the three-dimensional
regime for the first time. An initially incompressible (Alfvenic) MHD fluctuation generates,
by linear coupling, compressible (magnetoacoustic) fluctuations. In the initial stage of the
interaction, the efficiency of the coupling is enhanced by phase mixing of the
incompressible mode. In the developed stage of phase mixing,the interaction saturates and
both incompressible and compressible fluctuations approach a quasi-stationary state,which
has not been known before. The saturation level of density fluctuations is about 30 percent
of the initial Alfven amplitude. This level is small enough to escape detection by in-situ
measurements, which can explain high "Alfvenicity" of the solar wind.
Type:
talk
Any special equipment:
email:
tsikd@astro.warwick.ac.uk
Post held by presenter:
Postdoc
IP address
137.205.8.2
22-02-2002 14:43:16 155.198.17.120
Title of Presentation:
A Comparison between Ion Characteristics observed by the POLAR and DMSP spacecraft in the
High-Latitude Dayside Magnetosphere.
Presenting Author:
T.J. Stubbs
Other author(s):
T.J. Stubbs (1), P.J. Cargill (1), M. Lockwood (2), M. Grande (2), B. Kellett (2), C. Perry
(2).
Institute(s) of each author:
(1) Imperial College, London, U.K.,(2) Rutherford Appleton Laboratory, Oxon., U.K.
Abstract:
The convection dominated regions of the magnetosphere map to high invariant latitudes above
the poles of the Earth. Here we use the total ion signature, observed by CAMMICE MICS on board
the POLAR spacecraft, to relate magnetospheric ion populations to the precipitating ion fluxes
observed in the topside ionosphere by DMSP satellites (Newell and Meng, 1992). We do this by
plotting the total ion flux occurrence probabilities as a function of invariant latitude and
magnetic local time. We characterise the MICS ion spectra by both the peak in the differential
energy flux and average energy. The former allows comparison with the Stubbs et al., (2001)
survey of ions of solar wind origin within the high latitude magnetosphere, which used He2+
ions as a tracer; the latter allows comparison with the Newell and Meng survey of plasma
characteristics using DMSP data. Total ion fluxes are typically dominated by protons, we have
shown qualitatively that the occurrence distributions are consistent with those of ions of
solar wind origin. The differences in observed energy can be attributed to acceleration
processes at the magnetopause and in the tail. For average energies of around 1 keV, the total
ion occurrence distributions were centred in the pre-noon sector, thus relating to open field
lines features (LLBL/cusp/mantle). At higher energies (around 10 keV), the distribution tended
toward the auroral oval with no clear distinction between the regions defined by Newell and
Meng (e.g. CPS and BPS).
Type:
talk
Any special equipment:
email:
tj.stubbs@ic.ac.uk
Post held by presenter:
Postdoc
IP address
155.198.17.120
22-02-2002 14:53:11 128.40.72.254
Title of Presentation:
Cluter/PEACE observations of entry layer, boundary layer and cusp convection during an
interval of southward IMF.
Presenting Author:
Krauklis I.
Other author(s):
I. Krauklis, A.N. Fazakerley, C.J. Owen, P.J. Carter, M.W. Dunlop, M.G.G.T. Taylor, P.
Travnicek, A.J. Coates, R.J. Wilson, S. Szita,R.J. Wilson
Institute(s) of each author:
I. Krauklis, A.N. Fazakerley, C.J. Owen, P.J. Carter, M.G.G.T. Taylor,A.J. Coates, R.J.
Wilson, S. Szita, R.J. Wilson.,Mullard Space Science Laboratory, Department of Space and
Climate Physics,University College London, Holmbury St. Mary, Dorking, Surrey, RH5 6NT,
United Kingdom.,M.W. Dunlop.,Blackett Laboratory, Imperial College of Science Technology and
Medicine, Prince Consort Road,London SW7 2BW.,P. Travnicek.,Department of Space Physics,
Institute of Atmospheric Physics, AS CR,Bocni II/1401, CZ-14131 Prague, Czech Republic.
Abstract:
On the 16th of March 2001 the Cluster spacecraft made an inbound crossing of the dayside
southern magnetosphere close to 1200 MLT. During this crossing the IMF clock angle was
southrward and duskward. The spacecraft observed the magnetopause, entry layer, boundary
plasma sheet, boundary layer and cusp regions. Analysis of the differnces of the observation
times of various strutures within these magnetospheric regions revealed motion consistent
with convection due to sub-solar reconnection. In the entry layer, boundary layer and cusp
regions the mean Vy component velocity was duskward and Vz component was southward consistent
with subsolar reconnection with a finite positive IMF By component. The mean Vx component
velocity in the boundary layer and cusp regions was anti-sunward, also consistent with
sub-solar reconnection. The mean Vx component in the entry layer was sunward the magnetic
field, in this region, had a northward component, mapping the convection electric field along
the magnetic field to the entry layer in the noon-midnight meridian would result in a
convection velocity with a sunward component. The similarity in the velocities in the
boundary layer and cusp regions indicates that for southward IMF the boundry layer is on open
field lines.
Type:
nopref
Any special equipment:
email:
ick@mssl.ucl.ac.uk
Post held by presenter:
Academic Staff
IP address
128.40.72.254
22-02-2002 14:57:50 152.78.128.54
Title of Presentation:
Field-aligned current structure associated with ionospheric signatures of transient
magnetopause reconnection.
Presenting Author:
S.K. Morley
Other author(s):
S.K. Morley(1),M. Lockwood(1,2)
Institute(s) of each author:
1. Department of Physics and Astronomy, University of Southampton, UK.,2. Space Science
Division, Rutherford Appleton Laboratory, Chilton, UK.
Abstract:
The effect of the motion of newly-opened magnetic flux is transferred to the ionosphere
through field-aligned currents. We present a study of the structure of field-aligned currents
around patches of newly-opened flux produced by pulses in the magnetopause reconnection rate.
Predictions are made for a variety of orientations of interplanetary magnetic field and for
different combinations of satellite paths with respect to the open-closed field line boundary
(OCB) and the amplitude of the reconnection rate pulses. The latter combinations give cusp ion
dispersion signatures that are both 'stepped' and 'sawtooth' in form. The presence of these
field-aligned current structures may affect UV/green-line auroral forms as these are thought
to be associated with regions of upward field-aligned current on open field lines where the
plasma concentration in the lobe is low.
Type:
talk
Any special equipment:
email:
skm@phys.soton.ac.uk
Post held by presenter:
Postgrad
IP address
152.78.128.54
22-02-2002 15:04:22 64.210.241.103
Title of Presentation:
Rotational splitting of helioseismic modes in a magnetic solar model
Presenting Author:
Balazs Pinter
Other author(s):
Balazs Pinter,Roger New,Robert Erdelyi
Institute(s) of each author:
BP, RN: Sheffield Hallam University,RE: University of Sheffield
Abstract:
The splitting of helioseismic f- and p-modes is studied in the presence of a magnetic
atmosphere. The solar interior is in a steady state, with sub-photospheric plasma flow along
the equator representing solar rotation. The Cartesian geometry employed restricts the present
study to sectoral modes (m = +l and m = -l). We predict potentially observable effects.
Type:
talk
Any special equipment:
-
email:
b.pinter@shu.ac.uk
Post held by presenter:
Postdoc
IP address
64.210.241.103
22-02-2002 15:13:14 128.40.72.254
Title of Presentation:
CLUSTER OBSERVATIONS OF THE DYNAMIC HIGH ALTITUDE CUSP
Presenting Author:
Matt Taylor
Other author(s):
M.G.G.T Taylor (1), M. Dunlop (2), A. Vontrat-Reberac (3), B. Lavraud (4), I. Krauklis, (1),
C.J. Owen (1), A. Fazakerley (1), P. Travnicek (1,5),P.Decreau(6), P. Carter (1), A.J. Coates
(1), S. Szita (1), G. Watson (1), R.J. Wilson (1)
Institute(s) of each author:
(1) Mullard Space Science Laboratory, University College London, (2) Imperial College of
Science Technology and Medicine (3) CETP (Centre d'tude des Environnements Terrestre et Plan
taires) Velizy, France, (4) CESR (Centre d'tude Spatiale des Rayonnements), 31028 Toulouse
Cedex 4, France (5)Institute of Atmospheric Physics, The Academy of Sciences of the Czech
Republic, (6) LPCE / CNRS 45071 ORLEANS Cedex 2 FRANCE
Abstract:
The Cluster mission’s principal aim is to resolve the spatial-temporal ambiguity
associated with single point measurement by probing small scale 3-D spatial structure. Of
particular interest are the mid-high altitude (˜6-10 RE) magnetospheric cusps,where
Cluster’s four point measuring capability is addressing some of the long standing issues
raised by previous spacecraft missions in this region (e.g. HEOS, HAWKEYE and INTERBALL). On
26th February 2001, the spacecraft were outbound over the northern hemisphere, at
approximately 12 MLT, approaching the magnetopause through the high-altitude (and exterior)
cusp region. Due to macroscopic motion of the cusp, the spacecraft made multiple entries into
the exterior cusp region before exiting into the magnetosheath. Utilising particle, wave and
magnetic field measurements from the PEACE, CIS, WHISPER and FGM instruments on board the
Cluster spacecraft, we examine the dynamic behaviour and internal structure of the cusp and
associated boundary layers. Using position information, defining the relative spacecraft
locations, together with the timing of key features in the instrument data sets, we estimate
the morphology of the cusp and its response to a disturbed magnetosheath field.
Type:
nopref
Any special equipment:
email:
mggtt@mssl.ucl.ac.uk
Post held by presenter:
Postdoc
IP address
128.40.72.254
22-02-2002 15:29:17 194.80.32.12
Title of Presentation:
Substorm related changes in precipitation in the dayside auroral zone – a multi
instrument case study
Presenting Author:
Andrew Kavangh
Other author(s):
A.J.Kavanagh, F.Honary, I.W. McCrea, E. Donovan, J. Manninen, P.C. Anderson, E.E. Woodfield
Institute(s) of each author:
Lancaster University/Rutherford Appleton Laboratories,Lancaster University,Rutherford
Appleton Laboratories,University of Calgary,Sodankyla Geophysical Observatory,Aerospace
Corporation,University of Leicester.
Abstract:
A period (0600-1230 UT, 11/02/1997) of enhanced electron density in the D and E regions is
investigated using the EISCAT UHF radar, IRIS and other complementary instruments. Changes in
the precipitation spectra are compared with observations of solar wind pressure and IMF
changes by the GEOTAIL satellite and ULF waves measured by ground based pulsation
magnetometers. The possibility of gradient-curvature drifting electrons as the cause for the
enhanced electron density at event onset is presented with estimates of the electron energy,
apparently supported by the EISCAT data. Although some of the observations seem to support
this theory, a closer inspection of the energy spectrum calculated from EISCAT and from a pass
of a DMSP satellite casts doubt on the ability of the theory to explain all of the phenomena.
A large change in the precipitation spectrum in the latter half of the event is determined to
be due to ion precipitation dominating over electrons. The origin of these ions is discussed
and it is concluded that they are ring-current ions precipitating during the recovery stage of
a small geomagnetic storm.
Type:
talk
Any special equipment:
email:
a.j.kavanagh@lancs.ac.uk
Post held by presenter:
Postgrad
IP address
194.80.32.12
22-02-2002 15:47:41 144.32.128.132
Title of Presentation:
A storm-time study of magnetospheric plasma and electron densities using ground-based
magnetometer and IMAGE satellite data.
Presenting Author:
Zoe C. Dent
Other author(s):
Zoe C. Dent (1), I. R. Mann (1), F. W. Menk (2), J. Goldstein (3), L. G. Ozeke (1)
Institute(s) of each author:
(1) Department of Physics, University of York, Heslington, York, UK., (2) Department of
Physics, The University of Newcastle, Newcastle, NSW, Australia., (3) Department of Physics
and Astronomy, Rice University, Texas, USA.
Abstract:
Equatorial-plane plasma density profiles derived using ground-based magnetometer array data
are compared to electron densities observed in-situ by the Radio Plasma Imager (RPI)
instrument aboard the IMAGE (Imager for Magnetopause-to-Aurora Global Exploration) satellite.
This comparison spans a number of days in May 2001, allowing the plasmaspheric dynamics of
depletion and refilling to be determined throughout the course of a moderate geomagnetic
,storm. The interval was chosen for the good conjunction between the IMAGE satellite orbit
and the SAMNET (Sub-Auroral Magnetometer NETwork) and BGS (British Geological Survey)
ground-based magnetometer arrays in Northern Europe. Comparison of plasma mass densities to
electron number densities also provides information about the presence of heavy ion
populations.
Type:
talk
Any special equipment:
email:
zoe@aurora.york.ac.uk
Post held by presenter:
Postgrad
IP address
144.32.128.132
22-02-2002 15:51:40 194.80.32.12
Title of Presentation:
IRIS observations of cosmic noise absorption pulsations
Presenting Author:
Andrew Senior
Other author(s):
A. Senior, F.Honary
Institute(s) of each author:
Lancaster University
Abstract:
Data from the Imaging Riometer for Ionospheric Studies (IRIS) at Kilpisjrvi, Finland (69.05N,
20.79?E) were used to explore the occurrence of absorption pulsations in the Pc5 band. A
correlation between these pulsations and solar wind speed is presented. It is found that the
occurrence of absorption pulsations is increased during episodes of high solar wind speed.
This evidence agrees with magnetometer observations of Pc5 pulsation generation under these
conditions. Case studies are presented exhibiting field line resonance and impulse driven
characteristics in the riometer data. Pulsations in the Pc4 band were also investigated in
particular to explore the possibilities of imaging riometer data in cases of ULF waves having
high azimuthal wave numbers that render them difficult to observe by ground based
magnetometers.
Type:
talk
Any special equipment:
email:
a.senior@lancs.ac.uk
Post held by presenter:
Postgrad
IP address
194.80.32.12
22-02-2002 15:53:19 144.32.34.91
Title of Presentation:
Quarter wavelength poloidal ULF waves: A comparison between theory and observation.
Presenting Author:
Louis Ozeke
Other author(s):
Louis G. Ozeke and I.R.Mann
Institute(s) of each author:
York University
Abstract:
By numerically solving the guided poloidal Alfven wave equation, we show that the values of
the ionospheric Pedersen conductivities at the ends of the resonant field line determine
which poloidal ULF wave harmonic modes are possible, and that maximum wave damping occurs
when the ionospheric Pedersen conductivity has a critical value. We show that if the
ionospheric Pedersen conductivities at the ends of the field line are both much greater than
the critical value then only half wavelength poloidal harmonic modes are possible. However,
if the ionospheric Pedersen conductivities are asymmetric at the ends of the field line, one
end being much smaller and the other end being much larger than the critical conductivity,
then half wavelength poloidal harmonic modes are no longer possible and only quarter
wavelength harmonic modes can exist. These quarter wavelength harmonic modes have a near
node in the magnetic perturbation amplitude at one end and an anti-node at the other end.
Stewart and Lanzerotti [1982] analysed a pulsation near L=4 with an unusually long period of
6 mins using two conjugate ground-based magnetometers, and showed that the pulsation
amplitude detected by the magnetometer in the southern hemisphere was approximately five
times larger than that detected by the conjugate magnetometer in the northern hemisphere. We
show that the properties of this pulsation may be explained by our quarter
wavelength solution of the guided poloidal wave equation.
Type:
talk
Any special equipment:
email:
louis@aurora.york.ac.uk
Post held by presenter:
Postgrad
IP address
144.32.34.91
22-02-2002 16:17:58 194.80.32.12
Title of Presentation:
Artificial Ionized Region in the Atmosphere and its Application
Presenting Author:
N.Borisov
Other author(s):
N.Borisov, A.Gurevich
Institute(s) of each author:
N.Borisov (Lancaster University/IZMIRAN),A.Gurevich (Lebedev Physical Institute)
Abstract:
Artificial Ionized Region (AIR) is supposed to be created in the atmosphere as a result of
breakdown in crossed beams of high power microwaves. The concentration of plasma in AIR can be
several orders of magnitude higher than the maximum natural plasma concentration in the
ionosphere. AIR is supported for a long time by periodic pulsed breakdown. AIR can be used as
an artificial mirror to provide TV and radio communication. One of the intersting applications
of AIR is local active experiments with ozone and other minor atmospheric constituents. The
main theoretical results are confirmed in laboratory experiments with strong microwaves.
Type:
talk
Any special equipment:
email:
n.borisov@lancaster.ac.uk
Post held by presenter:
Academic Staff
IP address
194.80.32.12
22-02-2002 16:26:33 144.32.34.92
Title of Presentation:
MHD waves in the magnetosphere: Their role in energy transport and dynamics
Presenting Author:
I.R. Mann
Other author(s):
I.R. Mann
Institute(s) of each author:
Department of Physics,University of York,Heslington,York,YO10 5DD.
Abstract:
MHD waves can be excited by a variety of plamaphysical processes throughout the magnetosphere.
This review will examine recent developments in understanding,the excitation, propagation,
damping and detection of these waves. Particular emphasis will be placed on recent
developments in understanding the morphology of global scale ultra-low frequency (ULF) MHD
waves, and their importance in relation to substorms, magnetosphere-ionosphere coupling
magnetotail-auroral coupling, and the dynamics of MeV energy electrons in the outer radiation
belt. The importance of ULF wave excitation and energy transport for solar wind-magnetosphere
coupling will also be discussed.
Type:
talk
Any special equipment:
email:
ian@aurora.york.ac.uk
Post held by presenter:
Academic Staff
IP address
144.32.34.92
22-02-2002 16:35:24 137.205.8.2
Title of Presentation:
MHD Modes of a current sheet
Presenting Author:
Fenwick C. Cooper
Other author(s):
Fenwick C. Cooper and Valery M. Nakariakov
Institute(s) of each author:
University of Warwick
Abstract:
We consider properties of MHD wave modes confined to magnetic interfaces separating two
plasmas with different parameters. The effects of oblique propagation and a magnetic field
shear are taken into account. We determine dispersion relations for these modes in the zero
and non-zero plasma-beta cases and undertake parametric studies of angular dependencies of
the phase and group speeds of the modes, and the mode localization. These results are then
extended to the slab case with two parallel interfaces. The results are relevant
to understanding of stability of current sheets and to MHD seismology of solar coronal
streamers.
Type:
talk
Any special equipment:
email:
cooperf@astro.warwick.ac.uk
Post held by presenter:
Postgrad
IP address
137.205.8.2
22-02-2002 16:45:04 194.66.1.60
Title of Presentation:
The Application of Computational Mechanics to the Analysis of Geomagnetic Data.
Presenting Author:
Mervyn P. Freeman
Other author(s):
Richard W. Clarke (1,2), Mervyn P. Freeman (1), and Nicholas W. Watkins (1)
Institute(s) of each author:
(1) British Antarctic Survey, Madingley Road, Cambridge, U.K.,(2) Queens' College, Cambridge,
U.K.
Abstract:
Computational mechanics (CM) is a formalism that has been proved to construct the minimal
model capable of statistically reproducing all the resolvable causal structure of any infinite
sequence of discrete measurements (be they scalar, vector, tensor, or descriptive). The size
of a model so defined, measured by a quantity termed statistical complexity is a reliable and
falsifiable indication of the amount of structure the data contain. The particular strengths
of this approach are that it enables the complexities and structures of different sets of data
to be quantifiably compared and that it directly discovers detailed causal structure within
those data. By examining data in this way it is possible to appreciate, in a well-defined
abstract sense, how a system actually functions and what scales are most important to it. This
information can then be used to optimise the efficiency of physically plausible models. We
adapt the ideal formalism of Computational Mechanics to make it applicable to a non-infinite
series of corrupted and correlated data, typical of most observed natural time series. The new
algorithm is then applied to analysis of a real geomagnetic time series measured at Halley,
Antarctica. Two principal components in the structure are detected that are interpreted as (a)
the diurnal variation due to the rotation of the earth-based station under an electrical
current pattern that is fixed with respect to the sun-earth axis and (b) the random occurrence
of a signature likely to be that of the magnetic substorm.
Type:
talk
Any special equipment:
No
email:
mpf@bas.ac.uk
Post held by presenter:
Other
IP address
194.66.1.60
22-02-2002 16:51:21 192.171.142.175
Title of Presentation:
The causes of long-term change in the aa index
Presenting Author:
Ellen Clarke
Other author(s):
Mark Cliverd (1), Toby Clark (2), Ellen Clarke (2), Henry Rishbeth (3) and Thomas Ulich (4)
Institute(s) of each author:
1 British Antarctic Survey,2 British Geological Survey,3 University of Southampton,4 Sodankyla
Observatory, Finland
Abstract:
The aa index provides the longest geomagnetic data set that can be used in the analysis of
magnetospheric and ionospheric phenomena. All phases of the solar cycle show increases in
storm activity since the end of cycle 14 in 1915. The activity increase does not appear to be
strongly associated with any instrumental, ionospheric or magnetospheric effects. Small
effects have been confirmed in the long-term change in ionospheric Pedersen and Hall
conductivities due the changing dipole moment of the Earth, but not due to increasing
greenhouse gases. Three instrumental effects have been identified where significant changes in
quiet-time conditions can be seen i.e. 1938, 1980, and 1997. These do not account for the
majority of the increase in aa. Noise levels for the aa index are now close to those seen at
the beginning of the dataset. The prime cause of the increase in storm activity is an increase
in solar activity. The average aa in cycle 23 should be about 1nT less than predicted from
previous cycles due to the reduction in baseline noise levels at the start of the cycle
(1997).
Type:
talk
Any special equipment:
email:
ellen.clarke@bgs.ac.uk
Post held by presenter:
Other
IP address
192.171.142.175
22-02-2002 16:57:13 138.38.32.87
Title of Presentation:
THE 8-HOUR TIDE IN THE ARCTIC MESOSPHERE & LOWER THERMOSPHERE
Presenting Author:
P.T.Younger
Other author(s):
,P.T.YOUNGER (1), D.PANCHEVA (2), H.R.MIDDLETON (2) & N.J.MITCHELL (1)
Institute(s) of each author:
1. University of Bath,2. University of Wales Aberystwyth
Abstract:
An all-sky VHF meteor radar at Esrange (68N, 21E) near Kiruna in Northern Sweden has been used
to investigate the 8-hour tide in the Arctic mesosphere and lower thermosphere. We present a
climatology of the 8-hour tide over the period August 1999 to April 2001. The tide appears to
be a persistent feature of the Arctic atmosphere, although a large day-to-day variability of
the tidal amplitude is observed. At times the 8-hour tide reaches amplitudes over 30 ms-1. The
amplitude of the tide increases with height across the observed height range of ~80-100 km.
Monthly mean tidal amplitudes range from < 2ms-1 to values as large as 10ms-1. A clear
seasonal behaviour is apparent with maximum amplitudes observed in the Autumn. Vertical
wavelengths are shortest in winter and spring (25-35 km) and longest in summer and autumn
(50-90 km). At least on some occasions the vertical wavenumber relationships between the 8-,
12- and 24-hour tides suggests that the 8-hour tide is being generated by non-linear
interaction between the 12- and 24-hour tides.
Type:
talk
Any special equipment:
email:
eeppty@bath.ac.uk
Post held by presenter:
Postgrad
IP address
138.38.32.87
22-02-2002 16:59:59 138.38.32.87
Title of Presentation:
Global Scale Tidal Variability and the Coupling of Tides and Planetary Waves
Presenting Author:
N.J.Mitchell
Other author(s):
N.J.Mitchell, D.Pancheva, M.E.Hagan, A.H.Manson, C.E.Meek, Y.Luo, Ch.Jacobi, D.Kuerschner,
R.R.Clark, W.Hocking,J.MacDougall, G.O.L.Jones, R.A.Vincent, I.M.Reid, W.Singer,K.Igarashi,
G.I.Fraser, T.Nakamura, T.Tsuda, Yu.Portnyagin,E. Merzlyakov, A.N.Fahrutdinova, A.M.Stepanov,
L.M.G. Poole,S.B.Malinga, B.L.Kashcheyev and A.N.Oleynikov
Institute(s) of each author:
University of Bath
Abstract:
PSMOS Experiment Number 1: Global Scale Tidal Variability ran an international campaign of
observations in June-August of 1999. The objective of the campaign was threefold: 1. To
characterise and distinguishing between the temporal and spatial variability of MLT-region
tides. 2. To investigate the latitudinal and longitudinal structure of the tides. 3. To
investigate the role of wave-wave interactions in tidal variability, with a particular focus
on the role of non-linear planetary-wave/tidal interactions. The campaign yielded an
excellent data set and this paper will present some highlights of the analysis to date. In
particular, comparisons of the tides with the Global Scale Wave Model have revealed a
generally good agreement with the amplitude and phase of the 24-hour tide, but significantly
larger amplitudes than predicted in the case of the 12-hour tide in summer at
high-latitudes. Modulation of tides by planetary waves was observed to be particularly strong
in the case of the 10-day and 16-day waves in summer, and the zonal wavenumbers of the
secondary waves appear to be in good agreement with the predictions of non-linear theory.
Type:
talk
Any special equipment:
Large brandy beforehand please
email:
eesnjm@bath.ac.uk
Post held by presenter:
Academic Staff
IP address
138.38.32.87
22-02-2002 17:11:32 193.61.213.130
Title of Presentation:
Dissipation of ion cyclotron waves by minor ions and plasma heating in coronal funnels
Presenting Author:
Xing Li
Other author(s):
Xing Li
Institute(s) of each author:
Department of Physics, University of Wales, Aberystwyth
Abstract:
Plasma heating in coronal funnels by ion cyclotron waves is investigated. Three major species,
protons, electrons and alpha particles are considered in the model. Ion cyclotron waves are
able to heat the corona from 50000 to above 1 million degrees by directly heating alpha
particles only. The strong Coulomb coupling between alpha particles and protons, and protons
and electrons makes it possible that protons and even electrons are heated to above 1M
degrees even though only alpha particles dissipates the waves. It is shown that an
equilibrium may be not established between alpha particles and protons even in the
transition region. However, they still reach an equilibrium at the bottom of the corona.
Type:
talk
Any special equipment:
No
email:
xxl@aber.ac.uk
Post held by presenter:
Academic Staff
IP address
193.61.213.130
22-02-2002 17:16:54 143.210.44.149
Title of Presentation:
Ionospheric signatures of high m ULF waves as measured by the DOppler Pulastion Experiment
(DOPE)
Presenting Author:
L.J.Baddeley
Other author(s):
L.J.Baddeley, T.K.Yeoman, D.M.Wright
Institute(s) of each author:
Leicester University
Abstract:
Ground observations of high m ULF waves in the morning sector have often been difficult to
undertake due to the small scale sizes of the ionospheric perturbations. The one class of such
events with a distinct ground signature, Giant Pulsations (Pgs), occur only rarely.
Previously, studies focused on Pgs and measurements of other classes of high m waves made by
spacecraft. This has resulted in only a few observations, and the limited case studies carried
out suggest a drift-bounce resonance interaction is the cause of the morning sector waves. The
DOppler Pulsation Experiment (DOPE), located at Troms, has demonstrated its ability to view
these small scale size ionospheric perturbations by measuring the bulk motion of the
ionosphere caused by the vertical component of the E-cross-B drift associated with ULF waves.
Since October 1999, DOPE has employed a multi-path technique, which allows not only greater
detection of these high m waves, but can also routinely quantify the azimuthal drift number, m
of the wave. The implications of recent results from DOPE for the genreation mechanisms of
morning sector high m waves will be discussed.
Type:
talk
Any special equipment:
email:
ljb14@ion.le.ac.uk
Post held by presenter:
Postgrad
IP address
143.210.44.149
22-02-2002 17:28:25 155.198.17.120
Title of Presentation:
CLuster observations of structures at quasi-parallel shocks
Presenting Author:
E. A. Lucek
Other author(s):
E. A. Lucek (1), T. S. Horbury (1), M. W. Dunlop (1), A. Balogh (1), S. J. Schwartz (2), I.
Dandouras (3), H. Reme (3)
Institute(s) of each author:
(1) Imperial College, London, UK,(2) Queen Mary College, London, UK,(3) CESR, Toulouse,
France
Abstract:
Magnetic field enhancements and regions of disturbed magnetic field are a key feature of
quasi-parallel shocks. We analyse Cluster magnetic field and plasma data from several
quasi-parallel shock crossings and compare the characteristics of isolated large-amplitude
magnetic field structures (SLAMS) with extended regions of disturbed magnetic field. At
separation scales of several hundred km the spacecraft observe different signatures which
might reflect either the typical scale size of the structures, or the existence of
sub-structure within them. Observations of individual SLAMS also suggests that they are not
planar on these scales. We use results from the study of individual SLAMS as context for a
statistical analysis of the magnetic field pulsation regions, and use the level of correlation
between different pairs of spacecraft to infer likely scale sizes and orientations of the
structures.
Type:
nopref
Any special equipment:
No
email:
e.lucek@ic.ac.uk
Post held by presenter:
Postdoc
IP address
155.198.17.120
22-02-2002 18:05:23 193.61.213.130
Title of Presentation:
A Three-fluid, 16-moment Gyrotropic Fast Solar Wind: The Effects of He++
Presenting Author:
Lorraine Allen
Other author(s):
Lorraine Allen, Xing Li
Institute(s) of each author:
UWA (University of Wales, Aberystwyth)
Abstract:
We present a 16-moment, three-fluid description of the solar wind consisting of electrons,
protons, and alpha particles. We assume gyrotropic flow (transport across the magnetic field
is neglected) described by the density, velocity, temperature, and parallel heat conductive
fluxes from the parallel and perpendicular directions for each particles species. The model
incorporates the effects of collisions and of the spiral magnetic field. It allows for
non-radial divergence of the magnetic field and heating and momentum addition to the
particles. For solar wind solutions consistent with empirical constraints, we study the heat
conductive fluxes of the particle species in comparison with the classical (collision
dominated) Spitzer-Harm values. We investigate the contribution the alpha particles make to
the solar wind heat flux and how the heat fluxes affect the species temperature profiles.
Type:
nopref
Any special equipment:
email:
loa@aber.ac.uk
Post held by presenter:
Academic Staff
IP address
193.61.213.130
22-02-2002 18:51:06 193.61.213.130
Title of Presentation:
The solar wind at solar maximum and its origin at the Sun
Presenting Author:
Shadia Rifai Habbal
Other author(s):
Institute(s) of each author:
University of Wales Aberystwyth
Abstract:
Spectroscopic and broadband white light measurements in the inner corona have led to
significant and surprising findings regarding the properties of the different ion species
forming the solar wind, and the sources of the wind at the Sun. This review will summarize
some of the striking results to have emerged from the past few years of SOHO observations
during solar minimum and maximum.
Type:
Any special equipment:
email:
sdh@aber.ac.uk
Post held by presenter:
Academic Staff
IP address
193.61.213.130
22-02-2002 21:23:01 213.1.184.147
Title of Presentation:
An iron resonance lidar at Rothera, Antarctica
Presenting Author:
Martin J Jarvis
Other author(s):
M. J. Jarvis, C. S. Gardner, P. E. Espy and M. A. Clilverd
Institute(s) of each author:
British Antarctic Survey, University of Illinois, British Antarctic Survey, British Antarctic
Survey
Abstract:
An iron resonance lidar designed to study the summer mesopause region has operated at South
Pole (90S) for 2 years. It is now in Cambridge and will be shipped to Rothera Research Station
(68S, 68W) on the Antarctic Peninsula for deployment and operation from January 2003. This
talk describes the lidar and demonstrates its capabilities and objectives.
Type:
talk
Any special equipment:
email:
m.jarvis@bas.ac.uk
Post held by presenter:
Academic Staff
IP address
213.1.184.147
22-02-2002 21:30:34 213.1.184.147
Title of Presentation:
Using riometers to observe gravity waves in the mesosphere.
Presenting Author:
Martin J Jarvis
Other author(s):
M. J. Jarvis, J. Foster and R. E. Hibbins
Institute(s) of each author:
British Antarctic Survey, University of Cambridge, British Antarctic Survey
Abstract:
Riometers are traditionally used to study particle precipitation effects in the ionospheric
D-region. Narrow beam imaging riometers, however, can also observe the weak signatures of
gravity waves in the mesosphere. Unlike optical imaging, this opens up the possibility of
studying of mesospheric gravity waves in daylight ? an important requirement in the high
latitude summer where gravity waves drive the cold summer mesopause temperatures.
Type:
talk
Any special equipment:
email:
m.jarvis@bas.ac.uk
Post held by presenter:
Academic Staff
IP address
213.1.184.147
22-02-2002 21:42:46 213.1.184.147
Title of Presentation:
jhvjh
Presenting Author:
Other author(s):
Institute(s) of each author:
Abstract:
Type:
Any special equipment:
email:
Post held by presenter:
IP address
213.1.184.147
22-02-2002 22:15:45 128.18.144.80
Title of Presentation:
F-region aurora and its magnetospheric consequences
Presenting Author:
Joshua Semeter
Other author(s):
Joshua Semeter, Richard Doe, Craig Heinselman, Jeffrey Thayer and John Kelly
Institute(s) of each author:
SRI International, 333 Ravenswood Ave.,Menlo Park, CA 94025, USA
Abstract:
Above 200 km the ionospheric is characterized by long recombination times, strong coupling to
the magnetic field, and an upward-directed ambipolar flux. Perturbations to this plasma by
soft electron precipitation will have very different consequences compared with the
lower-altitude perturbations associated with the visible aurora. Slow recombination means that
even a moderate number flux can have a large time-integrated effect; magnetic coupling means
that density perturbations will remain fixed in the convection coordinate system; the
ambipolar electric field means that increasing ion density will increase the efficacy of ion
outflow to the magnetosphere. We have made detailed measurements of F-region auroral arcs
over Sondrestrom using a multispectral imager and the incoherent scatter radar. Using spectral
imaging of the O+(732nm) line, we found significant ion production above 400 km, with
corresponding plasma enhancements extending uniformly from 100 km to at least 300 km (the
maximum range of the radar). These features cannot be easily understood within the context of
a standard auroral model. We will discuss possible interpretations, as well as implications
for magnetospheric coupling.
Type:
talk
Any special equipment:
email:
Post held by presenter:
Academic Staff
IP address
128.18.144.80
23-02-2002 18:49:46 129.110.7.52
Title of Presentation:
Ion and Neutral Drifts in the Polar Upper Atmosphere
Presenting Author:
R.A. Heelis
Other author(s):
R.A. Heelis,D. McEwen,W. Guo
Institute(s) of each author:
University of Texas at Dallas,University of Saskatchewan,University of Saskatchewan
Abstract:
Continuous observations of ion and neutral flows in the polar cap F-region are used to examine
their response to changes in the solar wind drivers. We find that the ion and neutral gases
respond almost immediately to changes in the solar wind driver but the time scales are quite
different. The ion motion filters the solar wind drivers over time scales of less than 5
minutes and has a response time constant of about 20 minutes. The neutral gas filters the
solar wind driver over time scales of about 30 of minutes and has a response time scale of
about 75 minutes. These features are consistent with previous expectations and estimates of
the neutral ion collision time. They are displayed with high fidelity in several individual
instances.
Type:
talk
Any special equipment:
email:
heelis@utdallas.edu
Post held by presenter:
Academic Staff
IP address
129.110.7.52
24-02-2002 16:59:26 195.92.194.14
Title of Presentation:
AstroGrid: Connecting Solar Science with the Virtual Universe
Presenting Author:
Nicholas A Walton
Other author(s):
on behalf of the AstroGrid Consortium
Institute(s) of each author:
Institute of Astronomy,University of Cambridge,Madingley Road,Cambridge,CB3 0HA, UK
Abstract:
The AstroGrid (http://www.astrogrid.org) project is developing a virtual observatory
capability to support efficient and effective exploitation of key astronomical data sets of
importance to the UK community. It's initial focus is providing the necessary
data-grid infrastructure and data-mining tools to support data generated by projects such as
WFCAM, VISTA, e-MERLIN, SOHO and Cluster. The project remit addresses a wide range of
astronomical areas, including the Solar and STP realms. Key capabilities of AstroGrid are
discussed, highlighting areas where they will enable multi-disciplinary astronomy. For
instance, AstroGrid will provide tools to aid a closer linkage of helio-seismological,remote
sensing and in-situ solar data to facilitate a greater understanding of solar processes such
as its magnetic field. It will achieve this through delivery of its main goals; a working
datagrid,linking key databases coupled with high throughput analysis,exploration and
data-mining capabilities for interrogating those databases. This presentation discusses the
development and deployment plans of AstroGrid together with a short discussion of its longer
term focus,with an emphasis on how AstroGrid capabilities could facilitate linkages e.g.
between Solar and Astronomy and between Solar and STP science areas. AstroGrid's close
involvement in broader European initiatives, the Astrophysical Virtual Observatory (AVO) and
the European Grid of Solar Observatories (EGSO), is highlighted. The open nature of the
project, stressing the importance of its on-line presence in engaging the community, will be
noted.
Type:
talk
Any special equipment:
email:
naw@ast.cam.ac.uk
Post held by presenter:
Academic Staff
IP address
195.92.194.14
25-02-2002 10:32:56 143.167.5.216
Title of Presentation:
MHD Waves in flux tubes
Presenting Author:
Miguel Homem
Other author(s):
Miguel Homem,Robert von Fay-Siebenburgen
Institute(s) of each author:
University of Sheffield
Abstract:
The nature of oscillations in a magnetic cylinder embedded in a magnetic environment with a
steady flow present is investigated. It is shown that a strong enough flow can originate
backward propagating waves. The flow induces shifts in the cut-off values and phase-speed of
the waves. This is important to take into account in the observations made in the Sun, for
observational data has shown that steady flows are present in the Sun's atmosphere. When
backward propagating waves are present it is shown that these waves have negative energy, and
so they grow if energy is removed from the system (e.g. dissipation). Two cases are studied
for photospheric and coronal conditions. And it is shown that these negative energy waves can
be present in the Sun's atmosphere.
Type:
nopref
Any special equipment:
email:
m.homem@sheffield.ac.uk
Post held by presenter:
Postgrad
IP address
143.167.5.216
25-02-2002 10:43:29 194.66.1.228
Title of Presentation:
Whistler mode chorus and electron acceleration in magnetic storms - a ground-based study
Presenting Author:
A.J. Smith
Other author(s):
A.J. Smith and R.B. Horne
Institute(s) of each author:
British Antarctic Survey,Madingley Road,CB3 0ET,Cambridge
Abstract:
Whistler mode waves in the form of ELF/VLF chorus, are generated by electrons injected into
the magnetosphere during geomagnetic storms and substorms. Recently evidence has been found
suggesting that this chorus may play a role in the poorly understood acceleration process
which produces electron fluxes in the relativistic energy range (~MeV), sometimes known
as "killer electrons" which can damage space systems in space weather events. To investigate
this possible effect further, we studied chorus observed at a ground station (Halley,
Antarctica), which although it is more remote from the magnetospheric source regions, has a
larger field of view than an in-situ satellite-borne receiver and thus provides an alternative
and complementary perspective. We present and interpret the intensities of chorus in the 1-3
kHz frequency range seen before, during, and after large storms in which electron acceleration
has occurred. These wave power flux levels are compared with those expected on average for the
same local time and season, as computed statistically from 10 years of nearly continuous data
from the VELOX instrument.
Type:
talk
Any special equipment:
email:
a.j.smith@bas.ac.uk
Post held by presenter:
Academic Staff
IP address
194.66.1.228
25-02-2002 11:01:28 143.167.5.216
Title of Presentation:
MHD Waves in flux tubes
Presenting Author:
Miguel Homem
Other author(s):
Robert Ederlyi
Institute(s) of each author:
University of Sheffield
Abstract:
The nature of oscillations in a magnetic cylinder embedded in a magnetic environment with a
field-aligned steady flow equilibrium is investigated. The various well-known MHD modes
are found and are anlysed depending on the strenght of the equiulbrium bulk motion. The flow
induces shifts in the cut-off values and phase-speed of the waves. It is also shown that a
strong enough equilibrium flow can drag e.g. the backward (oe forward) propagating waves and
change their direction of propagation. This is efect important to take into account in light
of observations of MHD waves made in the Sun. When e.g. backward propagating waves are present
it is shown that these waves have negative energy, and so they grow if energy is removed from
the system (i.e. there is a dissipation). Two equilibrium cases are studied in particular:
flux tubes (i) photospheric, and (ii) coronal conditions. It is shown that these negative
energy waves can be present in the Sun's atmosphere.
Type:
nopref
Any special equipment:
email:
m.homem@sheffield.ac.uk
Post held by presenter:
Postgrad
IP address
143.167.5.216
25-02-2002 11:26:59 143.167.6.12
Title of Presentation:
Impulsive heating in solar coronal loops
Presenting Author:
Cesar A. Mendoza-Briceno
Other author(s):
Mendoza-Briceno, C. A., Erdelyi, R. and Sigalotti, L.
Institute(s) of each author:
Mendoza-Briceno, Cesar A.,Space & Atmosphere Research Center, University of Sheffield, S10
2TN, Sheffield, England, UK,and,Centro de Astrofisica Teorica, Universidad de los Andes,
Merida, Venezuela, Erdelyi, Robert,Space & Atmosphere Research Center, University of
Sheffield, S10 2TN, Sheffield, England, UK,and Sigalotti, Leonardo,Centro de Fisica,
,Instituto Venezolano de Investigaciones Cientificas, Altos de Pipe, Venezuela.
Abstract:
Parker (1988) suggested that the solar corona is heated by numerous small localized events
called nano-flares. High-resolution satellites (SOHO and TRACE) have shown a kind of very
small-scale activity at transition region temperatures (explosive events, micro-flares,
blinkers, etc.). These events may serve as the building blocks of the heating mechanism of the
solar atmosphere. Here, we present the results of a series of numerical simulations which
detail the response of the coronal plasma in a magnetic loop to micro-scale heating pulse. The
energy input pulse(s) are located near the footpoint where temperature is approx. 104 K at
periodical injection. It is found that these succesives energy inputs can maintain the plasma
along the loop at typical coronal temperatures. Implications of these results upon the latest
coronal loops observation will be discussed.
Type:
talk
Any special equipment:
LCD
email:
c.mendoza@sheffield.ac.uk
Post held by presenter:
Postdoc
IP address
143.167.6.12
25-02-2002 11:35:24 143.167.6.22
Title of Presentation:
What the nature of blinkers really are?
Presenting Author:
Daniel Marik
Other author(s):
Daniel Marik, Robert Erdelyi
Institute(s) of each author:
Space and Atmosphere Research Group,Department of Applied Mathematics,University of
Sheffield,S3 7RH,United Kingdom
Abstract:
The transition region blinkers are one of the most controversial phenomena in the lower solar
atmosphere observed in the past five years. According to our model these small-scale bright
intensity enhancements may play a significant role not only in the solar transition region
but even in the solar wind acceleration and the solar atmospheric plasma heating. They were
mainly found, e.g., in He I (584.33 Å), O III (599.52 Å), O IV (554.52 Å), O V
(629.73 Å) and Mg IX (368.06 Å), respectively (Harrison et al., 1997). Their typical
parameters are: the mean lifetime is approximately 16 s, the intensity enhancement ratios
are around 1.8, and the appearing frequency on the whole solar surface is at 1 - 20
s-1. Blinker events appear to be increases in density or filling factor rather then to be
increases in temperature. Most of the blinkers have repetitive nature and high percentage of
these events occur above regions where one magnetic polarity dominates. We have developed a
simple physical model of blinkers based on the process of magnetic reconnection. In the
present paper we show our results of solving the fully nonlinear, time-dependent,
dissipative, radiative 2-D MHD equations using a staggered mesh. By setting the initial
parameters describing blinkers we found propagating jets with similar properties found by
observations.
Type:
talk
Any special equipment:
email:
Post held by presenter:
Postgrad
IP address
143.167.6.22
25-02-2002 12:24:14 143.167.53.130
Title of Presentation:
Wavelet based spectral analysis of the atmospheric temperatures from 1600Bc to the present
time
Presenting Author:
Nasser M. K. Al-Hatmi
Other author(s):
Nasser M. K. Al-Hatmi, Misha Balikhin and Ian Bates
Institute(s) of each author:
ACSE, The University of Sheffield
Abstract:
Annual tree growth reflects the climatic conditions of the year and the width of annual tree
rings can be considered as an implicit function of the climate conditions. Various methods of
data analysis have been developed to reconstruct particular parameters such as temperatures
and moisture variability. One of the main advantages of tree ring related climatic data is
their high temporal resolution and rigid dating control. In the present work we used
reconstructed atmospheric temperatures for three locations: Tasmania, Yamal and Taymir.
Spectral analysis of these data reveals that drastic changes in the dynamics of the
temperature variations occurred in the southern hemisphere about 2000 years ago. Relations of
calculated temperature spectra to known solar periodicities are investigated.
Type:
talk
Any special equipment:
email:
coa98nma@sheffield.ac.uk
Post held by presenter:
Other
IP address
143.167.53.130
25-02-2002 16:41:10 143.167.52.41
Title of Presentation:
Isomagnetic Subshocks
Presenting Author:
M. Ruderman
Other author(s):
M. Ruderman, M. Balikhin
Institute(s) of each author:
The University of Sheffield
Abstract:
The structure of a collisionless shock for a Mach number larger than the first critical Mach
number M* have been studied in frame of MHD approximation with added anomalous resistivity. It
is shown in accordance with the previous theoretical results that an isomagnetic
subshock should occur for shocks with such Mavch numbers. It is shown that when resistivity
is the only dissipative process taken into account, a subshock is present at the end of the
magnetic ramp. However in case of adddtional dissipative processes subshock can be generated
in other parts of the ramp as well. We have calculated the amplitude of the subshock and
compared it with that obtained from observations.
Type:
talk
Any special equipment:
email:
m.s.ruderman@sheffield.ac.uk
Post held by presenter:
Academic Staff
IP address
143.167.52.41
25-02-2002 17:00:42 143.167.6.230
Title of Presentation:
The damping of coronal loop oscillations
Presenting Author:
Ruderman MS
Other author(s):
Roberts B
Institute(s) of each author:
University of Sheffield,University of St Andrews
Abstract:
Motivated by recent TRACE observations of damped oscillations in coronal loops, we consider
analytically the motion of an inhomogeneous coronal magnetic tube of radius a in a zero-beta
plasma. An initially perturbed tube may vibrate in its kink mode of oscillation but those
vibrations are damped. The damping is due to resonant absorption, acting in the inhomogeneous
regions of the tube, which leads to a transfer of energy from the kink mode to Alfven
(azimuthal) oscillations within the inhomogeneous layer. We determine explicitly the
decrement for a coronal flux tube whose plasma density varies only in a thin layer of
thickness l on the tube boundary. During the damping time (which is equal to the inverse of
the decrement of the global oscillation) most of the energy in the initial perturbation is
tranferred into a resonant absorption layer of thickness of order l(l/a) with motions in this
layer having an amplitude of order a/l times the initial amplitude. We apply our results to
the observations, suggesting that loop oscillations decay principally because of
inhomogeneities in the loop. Our theory suggests that only those loops with density
inhomogeneities on a small scale are able to support coherent oscillations for any length of
time, and so be observable. Loops with a more gradual density variation, on the scale of the
tube radius a, do not exhibit pronounced oscillations.
Type:
talk
Any special equipment:
email:
Post held by presenter:
Academic Staff
IP address
143.167.6.230
25-02-2002 17:16:51 143.167.53.130
Title of Presentation:
Cluster Observation of a quasi-electrostatic subshock
Presenting Author:
M. Balikhin(1)
Other author(s):
M.Balikhin (1), M. Dunlop(2), I. Bates(1), M. Ruderman(1), and H. Alleyne(1)
Institute(s) of each author:
(1) The University of Sheffield,(2) Imperial College
Abstract:
Electric field
measurements made on board the four Cluster-II satellites are used to estimate the spatial
scale of the electrostatic potential in the front of the terrestrial bow shock in the
quasi-perpendicular regime. High amplitude, electric fields (up to 70mV/m) were measured at
the shock fronts encountered on March 31, 2001. The main change in the cross-shock potential
took place on spatial scales of a few electron inertial lengths. Such small scales in the
electrostatic potential can be explained in the framework of the quasi-electrostatic sub-shock
concept. The high magnitude of the upstream magnetic field, which resulted in an unusually
small $\beta$ and moderate Mach numbers, created favourable conditions for the occurrence of
quasi-electrostatic sub-shocks in the shock front.
Type:
talk
Any special equipment:
email:
m.balikhin@shef.ac.uk
Post held by presenter:
Academic Staff
IP address
143.167.53.130
25-02-2002 17:25:12 143.167.53.130
Title of Presentation:
Wave Mode Identification using CLUSTER data
Presenting Author:
I. Bates
Other author(s):
I. Bates(1), M. Balikhin(1), M. Andre(2)
Institute(s) of each author:
(1)Space Systems Group, ACSE Department, University of Sheffield, U.K.,(2)IRFU, University of
Uppsala, Sweden.
Abstract:
The identification of plasma wave modes from dual satellite data is limited by the methods
used for finding wave propagation directions. These methods (e.g. minimum variance analysis)
impose strong limitations on the properties of the observed waves. The CLUSTER mission, with
its quartet of satellites, makes possible a method for determining wave propagation directions
without the limitations imposed by MVA. This method enables identification of wave modes
observed in electric field components. Such an identification was carried out for low
frequency waves, observed in the magnetosheath, measured by the EFW instrument.
Type:
talk
Any special equipment:
email:
i.bates@shef.ac.uk
Post held by presenter:
Postgrad
IP address
143.167.53.130
26-02-2002 11:47:28 130.246.132.27
Title of Presentation:
An update on the SOHO mission, the development of the STEREO mission and future plans for
Solar Orbiter
Presenting Author:
Richard A. Harrison
Other author(s):
Richard A. Harrison
Institute(s) of each author:
Rutherford Appleton Laboratory
Abstract:
SOHO has been in operation for over 6 years and has had a tremendous impact on our knowledge
of the Sun. Despite its age, the spacecraft and most instruments remain healthy and ESA is
discussing another mission extension to 2007. A report on the status of SOHO and future plans
will be given. In addition, a report on the development and nature of the STEREO mission will
be given. Due for launch in 2005,STEREO carries camera systems and an instrument from the UK
(RAL and Birmingham). The objective of STEREO is the observation and investigation of coronal
mass ejections from out of the Sun Earth line. Further in the future is the recently selected
ESA F-mission, Solar Orbiter, which was proposed by a team with a heavy UK involvement.
ESA's plans for Orbiter and the UK role will be discussed.
Type:
talk
Any special equipment:
email:
r.harrison@rl.ac.uk
Post held by presenter:
Academic Staff
IP address
130.246.132.27
26-02-2002 13:48:10 138.251.201.34
Title of Presentation:
A Flux Tube Tectonics Model for Coronal Heating
Presenting Author:
ER Priest
Other author(s):
Institute(s) of each author:
St Andrews University
Abstract:
we explore some of the consequences of the Magnetic Carpet for coronal heating. Since the
photospheric flux is concentrated into many small sources, the overlying coronal magnetic
field will be highly complex and will contain myriads of separatrix surfaces, dividing the
flux from each source. As the sources move around we suggest that current sheets and
dissipation are driven at the separatrix surfaces. A consequence of this is that large coronal
loops should exhibit enhanced heating near their feet in the carpet and that the upper parts
of the loops should be heated rather uniformly but less strongly.
Type:
talk
Any special equipment:
email:
eric@mcs.st-and.ac.uk
Post held by presenter:
Academic Staff
IP address
138.251.201.34
26-02-2002 14:00:36 193.61.213.131
Title of Presentation:
NLTE modelling of helium lines in quiescent solar prominences
Presenting Author:
Nicolas LABROSSE
Other author(s):
Nicolas LABROSSE (1) and Pierre GOUTTEBROZE (2)
Institute(s) of each author:
(1) The University of Wales, Aberystwyth,Department of Physics,Aberystwyth,Ceredigion SY23
3BZ,UK,(2) Institut d'Astrophysique Spatiale,Universite Paris XI, Bat. 121,91405 ORSAY
CEDEX,FRANCE
Abstract:
Despite its great importance, no theoretical calculations on a large range of the observed
helium spectrum in quiescent prominences have been performed out of Local Thermodynamic
Equilibrium (LTE) since previous work by Heasley and co-workers (published between 1974 and
1983). This work aims at carrying out new non-LTE computations considering Partial
Redistribution in Frequency for the formation of the main EUV resonance lines of helium. We
compute the helium spectrum emerging from a one-dimensional prominence, considering 34
energy levels in the multi-ion helium model (He I + He II + He III). This theoretical study
shows the different effects of the physical parameters of our models (temperature, gas
pressure, slab thickness, microturbulent velocity) on the helium level populations, as well
as on the emitted intensities. We also show the effect of the inclusion of a transition
region between the prominence core and the corona, compared to isothermal-isobaric models.
Preliminary comparisons with SUMER and CDS observations have also been made, thus leading to
a diagnostic of the observed structure. The numerical non-LTE diagnostic tool which is now
available brings a considerable improvement for the interpretation of observations and
allows a better understanding of the formation of the helium spectrum in prominences. Some
perspectives will be given.
Type:
nopref
Any special equipment:
email:
nll@aber.ac.uk
Post held by presenter:
Postdoc
IP address
193.61.213.131
26-02-2002 15:20:15 143.167.5.136
Title of Presentation:
MHD waves and instabilities at the outer magnetospheric boundary
Presenting Author:
Youra Taroyan
Other author(s):
Youra Taroyan and Robert Erdélyi
Institute(s) of each author:
Department of Applied Mathematics,The University of Sheffield
Abstract:
Surface waves at the outer boundary of the magnetosphere are studied and classified in the MHD
(magnetohydrodynamic) approximation. The boundary separating the fast flowing magnetosheath
from the homogeneous magnetosphere is asumed to have a finite thickness where the density,
magnetic field and flow velocity undergo a continuos change in the direction across the
magnetopause. In the absence of flow,the interaction of the surface waves with the local Alven
waves leads to resonant damping of both types of waves. However, in the presence of flow the
waves become resonantly unstable. It is shown that the resonant flow instability requires flow
velocities below the Kelvin-Helmholtz threshold and can be a viable mechanism for the
energisation in the magnetosphere. The effects of pressure anisotropy in the magnetosheath are
also studied.
Type:
talk
Any special equipment:
No
email:
y.taroyan@sheffield.ac.uk
Post held by presenter:
Postgrad
IP address
143.167.5.136
27-02-2002 14:55:12 137.108.72.23
Title of Presentation:
HESSI Imageing of Solar Flares
Presenting Author:
Benjamin A. C. Eves
Other author(s):
Benjamin A. C. Eves,Andrew Conway
Institute(s) of each author:
Open University
Abstract:
Maximum Entropy Methods (MEMs) provide a method of image reconstruction for Fourier synthesis
imagers such as HESSI,where only incomplete image information is available. The question
remains as to how representative these reconstructions are of the original flare, as very
different images can be obtained from the same modulation profile. To this end we have run
numerous reconstructions of some test cases, for both MEM_SATO and MEM_VIS, two of the MEM
,algorithms for use with the HESSI data. The main aim is to assess the effect the initial
entropy multiplier has on reconstructions of sources of various brightness and compactness.
We present these results and use them to interpret some of the preliminary observations from
HESSI.
Type:
poster
Any special equipment:
No, other than somewhere to put the poster.
email:
b.a.c.eves@open.ac.uk
Post held by presenter:
Postgrad
IP address
137.108.72.23
28-02-2002 17:03:20 130.88.96.65
Title of Presentation:
Probing nanoflare heating with the X-ray variability of coronal loops
Presenting Author:
G Vekstein
Other author(s):
R Jain and G Vekstein
Institute(s) of each author:
Dept. of Physics, UMIST, Manchester
Abstract:
If small-scale energy release events dubbed "nanoflares" contribute to the heating of the
solar corona, they may be too small to be recognised individually. Therefore, to test the
nanoflare scenario of coronal heating, it is necessary to consider statistical
characteristics of active regions, which result from a large number of random impulsive
heating events. This talk aims to demonstrate how such an approach allows one to predict
various signatures of X-ray coronal loops (average temperature, emission measure, filling
factor, etc)without specifying particular details of the heating events. It is also shown
how the energy of individual nanoflares can be deduced from the observed fluctuations of the
coronal X-ray intensity.
Type:
talk
Any special equipment:
email:
g.vekstein@umist.ac.uk
Post held by presenter:
Academic Staff
IP address
130.88.96.65
01-03-2002 10:43:33 143.167.6.115
Title of Presentation:
Comparison of the He+ layer seen above Arecibo with the CTIP model and the DMSP satellites
Presenting Author:
C.R. Wilford
Other author(s):
C.R. Wilford (1), R.J. Moffett (1), J.M. Rees (1), G.J. Bailey (1), S.A. Gonzalez (2), R.A.
Heelis (3)
Institute(s) of each author:
(1) University of Sheffield,(2) Arecibo Radio Observatory, Puerto Rico,(3) University of Texas
at Dallas (UTD), USA
Abstract:
Improvements in the measuring techniques used at the Arecibo incoherent scatter radar (ISR)
now mean that it is possible to make accurate measurements of the light ion concentrations up
to altitudes of approximately 2000 km. Data from the Arecibo radar show the formation of night
time He+ layers at an altitude of approximately 800 km. Data from DMSP satellites are also
available. The CTIP model is used to study phenomenon of He+ layering. Results from Arecibo
are presented and compared with CTIP model results.
Type:
talk
Any special equipment:
email:
c.wilford@sheffield.ac.uk
Post held by presenter:
Postgrad
IP address
143.167.6.115
07-03-2002 12:21:33 138.251.201.67
Title of Presentation:
Swing coupling between fast magnetosonic and Alfvén waves
Presenting Author:
T. Zaqarashvili1,2
Other author(s):
B. Roberts1
Institute(s) of each author:
1. Department of Mathematics, University of St Andrews, Scotland,2. Abastumani
Astrophysical Observatory, Georgia
Abstract:
We suggest a mechanism of energy transformation from fast magnetosonic waves propagating
across a magnetic field to Alfvén waves propagating along the field. The mechanism is
based on swing wave-wave interaction (Zaqarashvili 2001). The standing fast magnetosonic waves
cause a periodical variation in the Alfvén speed, with the amplitude of an Alfvén
wave being governed by Mathieu's equation. Consequently, sub-harmonics of Alfvén waves
with a frequency half that of magnetosonic waves grow exponentially in time. It is suggested
that the energy of nonelectromagnetic forces, which are able to support the magnetosonic
oscillations, may be transmitted into the energy of purely magnetic oscillations. Possible
astrophysical applications of the mechanism are briefly discussed.
Type:
talk
Any special equipment:
email:
temury@mcs.st-and.ac.uk
Post held by presenter:
Postdoc
IP address
138.251.201.67
13-03-2002 11:18:11 155.198.17.120
Title of Presentation:
Time-distance helioseismology of subsurface flows
Presenting Author:
S J Hughes
Other author(s):
M J Thompson
Institute(s) of each author:
IC,IC
Abstract:
Time-distance helioseismology is a powerful technique for resolving local flows and stucture
in the upper part of the solar convection zone. We examine the present state of the technique
with regard to meridional flows. We review existing work and indicate how, with the benefit
of more advanced treatment of the wave dynamics, we are aiming to improve and extend these
results.
Type:
talk
Any special equipment:
email:
stephen.hughes1@ic.ac.uk
Post held by presenter:
Postgrad
IP address
155.198.17.120
Title of Presentation:
IRIS Observations of Solar Activity
Presenting Author:
S R Marple
Other author(s):
S. R. Marple, F. Honary, M. Friedrich
Institute(s) of each author:
Lancaster University; Lancaster University; Technical University, Graz, Austria
Abstract:
The Imaging Riometer for Ionospheric Studies (IRIS) observes many
aspects of solar activity, from both ends of the sun-earth
connection. Solar radio emissions observed by IRIS provide a measure
of solar activity at the far end of the connection. At our end of the
sun-earth connection solar effects can take several forms. Solar
particles travel through and interact with the magnetosphere and
ionosphere, where they may cause polar cap absorption. Solar EM
radiation (UV and X-rays) affect the ionosphere directly. IRIS
observations of all these effects are compared with solar measurements
as a function of solar cycle.
Type:
Talk preferred
Any special equipment:
No
email:
s.marple@lancaster.ac.uk
Post held by presenter:
Postdoctoral
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